Ceasefire on Borrowed Time: The Fragility of Great Power Mediation in the Thai-Cambodian Dispute

What began as a localised border dispute between Thailand and Cambodia now has the US and China competing, not in a proxy battle, but to play peacekeeper. For the time being, their stakes in the conflict are obscure. While their involvement enables mediation, it yields only a brittle truce at best. At worst, their involvement could sow the seeds for a more dangerous showdown ahead.

International media initially framed July’s escalation of the Thai-Cambodian fighting as a confrontation between a US ally and a Chinese-backed regime. This narrative hinged on Thailand’s status as a major non-NATO ally of the US — one that maintains close security alliances with Washington through joint drills like Cobra Gold and arms procurement, including the F-16 fighters used in strikes against Cambodian military targets. Cambodia, by contrast, was seen as a Chinese client state, reliant on Beijing for arms, infrastructure, and loans that have left it heavily indebted.

Most analysts were quick, and right, to dismiss this framing as an oversimplification. Compared to the South China Sea or the Korean Peninsula flashpoints, the Thailand–Cambodia border conflict currently lacks the geopolitical weight to fundamentally reshape regional security dynamics or draw global powers into combat. More importantly, the US-backed Thailand versus Chinese-backed Cambodia narrative overlooks both countries’ increasing closeness to China.

China — not the US — is Thailand’s largest partner in trade and tourism. Security ties between Thailand and China have also deepened, particularly since the 2014 coup, which strained US–Thai relations and pushed Thailand to lean more heavily toward Beijing. On the other hand, Cambodia’s relationship with Washington may be warmer than generally perceived. Cambodian Prime Minister Hun Manet’s West Point affiliation and reports of growing American activities around the Chinese-built Ream Naval Base. There are growing signs of warmer US-Cambodia ties. In December 2024, a US warship docked for the first time in nearly a decade at the base. US Defence Secretary Pete Hegseth will also be visiting Cambodia soon. For these reasons, casting the conflict simply as a proxy battle between the two major powers risks distorting its nature and gravely exaggerating the stakes of what is likely to remain a relatively contained border dispute, as was the case during the 2011 armed clashes.

Yet, the two major powers have capitalised on the conflict to assert their influence in Southeast Asia. China moved first, and soon after Cambodia’s 15 June dispute submission to the International Court of Justice — against Thailand’s preference — in response to a late-May gunfight near Chong Bok that killed one Cambodian soldier. On 11 July, China’s Foreign Minister Wang Yi declared at the ASEAN Foreign Ministers’ Meeting that China was “willing to uphold an objective and fair position and play a constructive role for the harmonious coexistence between Thailand and Cambodia.” As political scientist Pongphisoot Busbarat aptly observes, China’s interest may be to contain border instability that could jeopardise its Belt and Road Initiative, for which both Thailand and Cambodia are critical nodes. More broadly, successful mediation could help China rehabilitate its image in a region wary of its assertiveness and tendency to put “core interests” before regional stability.

… the more Thailand and Cambodia rely on the major powers, the less they invest in their own independent mechanisms, crucial for managing compliance on the ground.

But the US ultimately seized the spotlight. This may have been driven less by a coherent strategy than by US President Donald Trump’s Nobel Peace Prize bid, which is backed by Hun Manet. On 26 July, two days after clashes erupted near the Ta Muen Thom temple, Trump called both Hun Manet and Thailand’s acting Prime Minister Phumtham Wechayachai, warning that continued fighting could derail then-ongoing trade negotiations and subject both Thailand and Cambodia to a 36 per cent tariff. Trump’s intervention apparently did the trick. By month’s end, Thailand — which had initially refused third-party mediation — and Cambodia agreed to a ceasefire at peace talks formally brokered by ASEAN Chair Anwar Ibrahim in Malaysia, joined by the US as a “co-organiser” and China as an “active participant.” Both powers remained involved as observers alongside Malaysia on the final day of the General Border Committee meetings between Thai and Cambodian militaries in Kuala Lumpur in early August.

The episode suggests that the Thailand–Cambodia dispute has effectively become a stage for a diplomatic contest between two global superpowers, with ASEAN relegated to a largely ceremonial role that might not have materialised at all without the initiative of Malaysia as ASEAN Chair. Malaysia’s mediation, dominated by US and Chinese supervision, may have achieved a ceasefire, but it does not necessarily improve the prospects for a long-term resolution.

For one, any future negotiations could unfold under the shadow of great power involvement. This will create perverse incentives for Thailand and Cambodia to posture and perform for external audiences rather than engage in the quiet, technical dialogue necessary to restore even the pre-2025 status quo — let alone resolve the complex boundary demarcation issues rooted in ambiguous French colonial cartography. Put differently, the more Thailand and Cambodia rely on the major powers, the less they invest in their own bilateral mechanisms, which are crucial for managing compliance on the ground.

Another layer of complexity is Cambodia’s courtship of Trump. In an apparent rebalance of foreign relations away from China, Phnom Penh is making a bid to sustain a favourable trade deal with the US as its economy strains. On the streets of Phnom Penh, there are huge billboards lauding Trump’s role in achieving the ceasefire and monks carrying his portraits in a peace march. While Cambodia’s attempts to curry favour with the US president have been energetic, its landmine clearance on the border has been sluggish. The mines have injured several Thai soldiers since the ceasefire, and a fatality could reignite the fighting. Furthermore, the expectation of external intervention — and possible concessions for such backing — could counterproductively lead to hardening stances. Amid the intrinsic sharpening of Thailand–Cambodia divisions, the ceasefire durability rests almost entirely on sustained great-power attention, which is likely to wane in today’s restless world. This could mean that a fiercer confrontation could well be brewing.

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