A fresh outbreak of violence along the Thailand–Cambodia border has drawn intense international attention and placed Washington’s influence in Southeast Asia under renewed scrutiny as rival diplomatic currents from the United States and China shape efforts to manage the crisis.

After weeks of deadly clashes rooted in a long-standing territorial dispute, Bangkok and Phnom Penh agreed a new ceasefire on December twenty-seventh, bringing a temporary halt to hostilities that have claimed more than one hundred lives and displaced hundreds of thousands of civilians.

The renewed truce followed earlier peace efforts in which U.S. President Donald Trump played a prominent role by calling leaders in both capitals and conditioning aspects of U.S. diplomacy, including trade leverage, on the cessation of fighting.

Yet the October peace accord brokered in Kuala Lumpur — and backed publicly by Washington alongside Malaysian and Association of Southeast Asian Nations mediation — unraveled amid fresh fighting in December, underscoring the limitations of external influence over deep-rooted regional disputes.

 American diplomatic engagement in the dispute has been marked by highly visible interventions, including Trump’s personal public declarations of peace and his framing of the ceasefire in global leadership terms.

While Thailand’s government and military welcomed international support for de-escalation, observers noted that domestic political pressures and rising nationalism in both Thailand and Cambodia constrained the effectiveness of Washington’s leverage in stabilising the frontier and cementing lasting peace.

Analysts have described U.S. tactics as “carrot-and-stick,” blending diplomatic pressure with economic incentives or threats, while China’s approach has been characterised as quieter but persistent, focusing on regional dialogue platforms and direct mediation.

The broader strategic context has framed the conflict as more than a bilateral border dispute.

Thailand remains a longstanding U.S. treaty partner with deep defence and security links, while Cambodia has strengthened its ties with Beijing through extensive economic cooperation and strategic alignment.

This great power overlay complicates regional diplomacy, with both Washington and Beijing keen to avoid prolonged instability that could disrupt investment, supply chains and political influence across mainland Southeast Asia.

Despite high-profile peace overtures and a bespoke U.S.-brokered ceasefire, the December resurgence of clashes and subsequent Beijing-hosted talks illustrate how neither superpower can dictate outcomes on the ground without sustained regional consensus and effective local implementation.