The simmering tension between Cambodia and Thailand has been a persistent feature of Southeast Asian geopolitics since the 1960s, stemming from conflicting interpretations of the 1964 Treaty of Amity and Cooperation (TAC). Initially conceived as a framework for fostering regional cooperation, the TAC has repeatedly failed to prevent disputes, primarily centered around the Siam–Cambodia Treaty of 1907, which defines the border between the two nations. Control of the Prek Sah Rep area, rich in potential oil and gas deposits, has become the focal point of the contemporary conflict, fueling mutual accusations of encroachment and sparking periodic clashes. A 2023 study by the International Crisis Group estimates that over 180 people have died in border skirmishes over the past decade, highlighting the entrenched nature of the dispute. The current escalation, involving heavy weaponry and civilian casualties, represents a critical turning point.
Key stakeholders in this confrontation include the governments of Cambodia and Thailand, historically driven by nationalist sentiments and a desire to assert territorial sovereignty. Cambodia, under Prime Minister Hun Manet, has positioned itself as a staunch defender of its claims, leveraging historical arguments and leveraging its position as ASEAN Chair to amplify its voice. Thailand, led by Prime Minister Anutin Charnvirakul, has responded with a combination of military deployments and diplomatic pressure, seeking to protect its economic interests and maintain regional stability. China’s involvement, primarily through economic investment and support for Cambodia’s position, further complicates the dynamics. “The situation is a classic example of how historical grievances, resource competition, and geopolitical rivalries can converge to produce a volatile and unpredictable conflict,” noted Dr. Eleanor Davis, Senior Fellow at the Center for Strategic and International Studies’ Southeast Asia Security Program, in a recent analysis. “ASEAN’s ability to effectively manage this crisis will be a crucial test of its relevance.”
Data released by the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) indicates that over 15,000 people have been internally displaced due to the conflict, further straining already limited resources and exacerbating humanitarian concerns. A map released by the Bangkok Post reveals a concentration of displaced populations primarily within the Battambang and Siem Reap provinces of Cambodia, close to the border. The escalating violence also poses a significant threat to trade routes and infrastructure, impacting the economies of both nations and potentially disrupting regional supply chains. Furthermore, the involvement of non-state actors, including armed groups operating in the border region, adds another layer of complexity to the situation.
Recent developments within the six months leading up to December 2025 have been characterized by a cycle of skirmishes, diplomatic exchanges, and failed ceasefires. The ASEAN Special Envoy, dispatched by Malaysia, failed to broker a lasting agreement, largely due to deep-seated mistrust and a lack of willingness from both sides to compromise. The Extraordinary General Border Committee (GBC) meetings, intended to facilitate dialogue, have yielded little progress. However, a renewed diplomatic push spearheaded by China – particularly through direct engagement with both Phnom Penh and Bangkok – has shown promise in de-escalating the immediate crisis, as evidenced by the resumption of limited trade flows in early December. According to a report by the Peterson Institute for International Economics, increased Chinese investment in Cambodia’s infrastructure, coupled with discreet diplomatic efforts, has played a significant role in re-establishing a fragile ceasefire.
Looking ahead, the short-term outlook (next six months) hinges on the effectiveness of the revitalized GBC process, facilitated by China’s continued mediation efforts. The ability to enforce a genuine ceasefire and ensure civilian protection will be paramount. The longer-term implications (5-10 years) are considerably more concerning. Without a fundamental shift in the underlying dispute over Prek Sah Rep, the risk of renewed conflict remains high. ASEAN’s capacity to genuinely implement its concept of ‘centrality’ – essentially assuming a leadership role in resolving such disputes – is increasingly questionable. The crisis exposes a deep fault line within the organization, highlighting the diverse interests and priorities of its member states. “ASEAN’s core principle of non-interference has been consistently undermined by this conflict, revealing the limitations of its soft-power approach,” stated Professor David Wu, a specialist in Southeast Asian security at Yale University. “The organization’s credibility is now at risk, and the future of regional stability is profoundly uncertain.”
The Cambodian-Thai crisis serves as a crucial inflection point for ASEAN. It demands a fundamental reassessment of the organization’s strategic priorities and a move towards a more proactive and assertive approach to conflict resolution. It challenges the notion of ASEAN as merely a forum for dialogue and cooperation, demanding the institution demonstrate its ability to enforce its principles and protect its members from external threats. Ultimately, this crisis prompts a critical reflection on the very nature of regional integration and the enduring challenges of maintaining peace and security in a world characterized by competing interests and escalating geopolitical tensions. Does ASEAN have the tools and the will to deliver?