China’s Mediation Offer in the Thailand-Cambodia Border Dispute Sheds Light on Beijing’s Security Role in Southeast Asia

Fierce exchanges of artillery fire since July 24 shattered the fragile ceasefire along the Thai-Cambodian border, leading to a significant death toll, numerous injuries, and the displacement of tens of thousands of civilians.¹ While a ceasefire agreement has now been reached through efforts by the Association of Southeast Asian Nations (ASEAN) chair, Malaysia’s Prime Minister Anwar Ibrahim, it is notable both that China and the United States joined the talks as observers and that China had previously positioned itself as the potential peacemaker. China’s Foreign Minister Wang Yi told the ASEAN Foreign Ministers’ Meeting on July 11 in Kuala Lumpur that Beijing was prepared to “uphold an objective and fair position and play a constructive role for the harmonious coexistence between Thailand and Cambodia.”² The ongoing border crisis was, therefore, instructive about the possibilities and limits for China to translate the ambition of peacemaker that it has sometimes shown in the Middle East and Asia into meaningful action, and what such a role might signify for Southeast Asia’s balance of power especially.

China’s Mediation Bid

Beijing launched a diplomatic campaign with three significant moves in July. The first came during the ASEAN Foreign Ministers’ Meeting in Kuala Lumpur urging Bangkok and Phnom Penh to exercise “maximum restraint” and China’s offer of “objective and fair” good offices. Second, in the meeting with the Secretary-General of ASEAN Kao Kim Hourn in Beijing on July 25, Wang Yi framed the Thai-Cambodian dispute as a legacy of the Western colonial powers, implicitly casting China as the non-colonial problem-solver. He encouraged ASEAN to play a mediating role while reiterating China’s own readiness to assist.³ At the international level, the Chinese permanent representative at the United Nations suggested China was actively engaged in mediation.⁴

When Cambodia placed the matter before an emergency, closed-door UN Security Council meeting on July  25, China’s envoy urged de‑escalation but pressed the council to “support regional solutions,” a formulation that kept ASEAN where China wields growing influence at center stage.⁵ Although Trump’s pressure, which contributed to the quick ceasefire agreement, may overshadow China’s earlier diplomatic efforts, Beijing’s role in the peace process is not deterred. The recent meeting between Cambodian and Thai top diplomats, hosted by the Chinese Vice Foreign Minister on July 30, reflects China’s continued desire to stay engaged, albeit more discreetly and behind the scenes.⁶

Why Beijing Wants the Gavel

Several intersecting motives explain China’s activism. Above all, China has long promoted economic and infrastructure development in the Mekong subregion. The current conflict presents a significant challenge to connectivity between China and mainland Southeast Asia along the Belt and Road corridors that connect Kunming to Bangkok and feed Chinese-funded industrial zones on Cambodia’s coast. Protracted fighting jeopardizes both physical infrastructure and investor confidence. The border closure has already disrupted segments of regional supply chains and economic activities, impacts that are further aggravated by the ongoing crisis in Myanmar.

In the broader context of U.S.-China geopolitical rivalry, China’s potential role as a mediator could enhance its international stature and further entrench its influence in Southeast Asia. By taking the lead, Beijing sought to preempt other powers, especially the United States, Japan, and India, whose Indo-Pacific visions compete with its own.⁷ Against the backdrop of negative perceptions stemming from China’s actions in the South China Sea, a constructive role in mainland Southeast Asia could help to soften its image. This role also supports Beijing’s claim to be a responsible power and aligns with its rhetorical but ambiguous design of Xi Jinping’s so-called Global Security Initiative (GSI).

After all, Beijing’s role will underpin its political and geopolitical influence over both countries. Cambodia has already demonstrated strategic dependence on China in recent decades. And China has played a central role in modernizing Cambodia’s defense sector. This includes financial and infrastructure support for the renovation of the Ream Naval Base, as well as extensive military cooperation through joint drills, aid, and equipment transfers. These efforts have significantly enhanced Cambodia’s defense capabilities and confidence.

In Thailand, too, China’s economic footprint is noteworthy. China plays an important role in Thailand’s trade, tourism, infrastructure investment, and collaboration in green and digital economies. Although Thailand has been a military ally of the United States since the Cold War and holds the status of a Major Non-NATO Ally (MNNA), its relationship with Washington has experienced periodic strain driven by Thailand’s democratic backsliding and shifting American strategic interests away from mainland Southeast Asia. These dynamics have created space for Beijing to deepen its ties with Bangkok, particularly during periods of military rule. Beijing thus views this mediation effort as a test of its ability to nudge a hedging Thailand closer to its orbit.

Obstacles on the Ground

Yet the path to Beijing’s successful mediation in this or other contingencies in Southeast Asia remains challenging. Thai media has reported suspicions that the China factor may have played a role in provoking Phnom Penh’s most recent border claims, which began in May. Many pointed to China’s reiteration of its support for Cambodia and the Golden Dragon joint military exercise between China and Cambodia at the end of May as a symbol of Beijing’s support, bolstering the Cambodian government’s morale and confidence in its defense posture.⁸ Some Thai commentators have gone further, suggesting that China supplied weapons to Cambodia, thereby enabling the recent attacks on Thailand.⁹

Nor has Beijing’s offer of peacemaker been universally welcomed. While Thai leaders have politely acknowledged international offers to help de-escalate the conflict, they were firm in favor of bilateral talks before accepting Anwar’s mediation.¹⁰ Some analysts have speculated that China may in the future wish to utilize its newly established International Organization for Mediation (IOMed), based in Hong Kong, as a channel for engagement.¹¹ However, from Thailand’s perspective, this would have been unlikely to be politically palatable. Memories of contentious international arbitration, particularly the International Criminal of Justice’s (ICJ) rulings on border disputes with Cambodia in 1962 and 2013, have fostered deep public skepticism in Thailand toward external mediation.

At the same time, China’s moves may have sent the wrong signal to ASEAN, where Malaysia, as ASEAN chair, ultimately played a decisive role.¹² And such ASEAN efforts can collide with China’s attempt to assert its own stronger role, even as Beijing proclaims support for “regional solutions.”¹³ Therefore, overly assertive Chinese diplomacy can trigger backlash from both disputing parties and other ASEAN members wary of Beijing’s growing influence.

If the conflict escalates anew despite the ASEAN-brokered ceasefire, Washington could step in to assert its influence and push for a resolution. On July 26, and again amid the talks in Kuala Lumpur, President Donald Trump held phone conversations with the leaders of Thailand and Cambodia, as did Secretary of State Marco Rubio with his own counterparts, urging an immediate end to hostilities.¹⁴ Trump warned that no further tariff negotiations with the United States would proceed if the fighting persisted.¹⁵ With both nations currently subject to a steep 36 percent tariff, Trump’s ultimatum could have had a significant impact on the trajectory of the conflict.

Subsequently, the Thai and Cambodian leaders joined the talks in Kuala Lumpur on July 28.¹⁶ The meeting ultimately concluded with both sides agreeing to an immediate and unconditional ceasefire, effective at midnight. They also committed to utilizing bilateral mechanisms, including military-to-military dialogue and the General Border Committee (GBC), to address the situation.¹⁷ Sean O'Neill, the nominated ambassador to Thailand, later reinforced President Trump’s message, emphasizing that the conflict would not serve the interests of the Thai-U.S. alliance¹⁸ As a reward to Cambodia, Malaysia, and Thailand for accommodating President Trump’s demands, the United States reduced the reciprocal tariffs imposed on these three countries to 19 percent in the latest announcement.¹⁹ In light of this direct U.S. intervention, China’s role in the situation is unclear, given that the United States also attended the talks and Anwar sat in the mediator’s chair.

However, Beijing has not retreated from its mediating role. On the contrary, it remains a key player in the conflict despite Washington’s direct intervention. Its continued engagement, reflected in the recent talks held in Shanghai, signals a deliberate effort to shape outcomes in an informal and low-profile gesture. This continued involvement will help China safeguard its regional influence and balance the United States’ involvement. This calculated strategy underscores Beijing’s determination to assert its regional role while sidestepping confrontation.

 Considering opportunities and challenges, several avenues may stand out for China to pursue in the future. First, China should build trust among conflicting parties, especially Thailand. Through both the government and military channels, Beijing may have to reassure its commitment to the principle of non-interference and its impartiality in the conflict, emphasizing that it did not and does not favor Cambodia. Second, as China’s prospects of acting unilaterally as a peace broker diminish in light of the ASEAN and U.S. involvement and the recent ceasefire agreement, Beijing should pledge strong support for, or actively facilitate, an ASEAN-led mechanism for future mediation and trust-building between the two neighbors. It could support the ASEAN Chair and like-minded countries in persuading the conflicting parties to uphold the ceasefire agreement over the long term and to work toward durable de-escalation of tensions. By doing so, Beijing will reaffirm its previously stated commitment to regional solutions and help alleviate suspicions of power projection or dominance.

At the international level, China could propose that the UN recommend the establishment of a regional fact-finding body to promote a shared understanding of the conflict and encourage broader acceptance of its developments by all parties involved. However, such efforts should be grounded in ASEAN’s dispute settlement mechanisms, allowing Beijing to demonstrate its commitment to and promotion of ASEAN centrality. Beijing’s support for the United States’ call for a ceasefire was a prudent move, signaling its willingness to contribute to regional peace and stability despite underlying structural tensions. While such a move might appear to signal deference to American leadership in Southeast Asia, it could also serve to improve bilateral relations and ease geopolitical tensions between the two major powers in East Asia.

Risks of Beijing’s Activism for Southeast Asia

This mediation attempt was a critical test of China’s evolving security role in Southeast Asia. Historically, Beijing’s role has been viewed with suspicion, particularly in crises such as the ongoing conflict in Myanmar, where Chinese engagement has been seen as self-serving and disproportionately aligned with authoritarian actors. Despite efforts to broker peace, Myanmar’s junta has also sought to diversify its partnerships, most notably with Russia, highlighting potential long-term limits to China’s influence. ²⁰

In the case of Thailand and Cambodia, a successful ceasefire brokered by China would have reinforced the narrative that Beijing, not Washington, is the indispensable security manager of mainland Southeast Asia. However, this did not pan out. Any future failure to maintain neutrality could push Thailand closer to alternative partners such as Japan, India, or even the United States, and expose the limits of Chinese soft power.

For ASEAN, China's interest in a mediating role could deepen existing mistrust and pose a challenge to the bloc’s principle of centrality. Beijing has often been criticized for its Janus-faced approach to ASEAN—publicly affirming its support for ASEAN centrality while simultaneously pursuing bilateral arrangements, particularly in the context of maritime disputes in the South China Sea. In this light, any unilateral intervention by China in the Thai-Cambodian conflict could backfire, potentially undermining its position in other parts of the region where it is involved in similar disputes. If China again seeks to position itself as a third-party mediator in future land disputes such as the Thailand-Cambodia conflict, it will inevitably raise a broader question: would Beijing itself be comfortable with the very principle of external mediation in its own territorial disputes with neighboring countries?

Conclusion

The most recent round of the Thai-Cambodian border conflict has propelled China from a rhetorical supporter of ASEAN peace to a central player under intense scrutiny. A successful mediation in the future could convert economic leverage into geopolitical capital and advance China’s “peaceful rise” narrative. But any missteps, perceived bias, overreach, or misalignment with ASEAN, amid the fragile ceasefire brokered by ASEAN, could entrench skepticism, widen great power rivalries in the region, and place ASEAN in an uncomfortable crossfire.

In the weeks since tensions first erupted, the crisis has revealed several important insights into China’s role and the evolving regional order. First, it highlights that the United States has not faded from Southeast Asia, particularly in the security domain—even with the decline in U.S. influence in mainland Southeast Asia, the United States was still an observer at the Kuala Lumpur talks alongside China. Importantly, the United States has demonstrated a willingness to overtly exercise coercive diplomacy. This is evident in the potential direct impact of Washington’s tariff threats on the dynamics of the conflict, as well as in the pressure exerted on allies—particularly Thailand. alliances.

Second and more significantly, the situation underscores Southeast Asia’s continued reluctance to fully embrace China’s unilateral role or its model of peace and security management. While China’s power appears to be expanding across various domains in the region, especially amid shifts and uncertainty in American global leadership, this case highlights Beijing’s ongoing struggle to convert its growing capabilities into effective influence. Mistrust and suspicion toward China continue to cast a long shadow over its regional ambitions.

However, the most encouraging outcome of the recent talks in Malaysia, which led to a ceasefire agreement, is the visible cooperation between the United States and China as joint supporters of the negotiations. This reflects the kind of engagement the region hopes to see. Both powers play pivotal roles in shaping the regional architecture, and their collaboration is essential for maintaining its stability. In contrast, ongoing geopolitical tensions between them have heightened uncertainty and posed significant risks to all nations in the region, threatening both peace and long-term prosperity.