The incessant rumble of heavy machinery, combined with the sporadic bursts of gunfire echoing across the Cardamom Mountains, paints a stark picture of escalating tensions along the Cambodian-Thai border. Satellite imagery reveals a significant increase in construction activity near the disputed 200km maritime border, coinciding with a sharp rise in reported clashes between Cambodian security forces and Thai military units. This simmering conflict, rooted in historical claims, resource competition, and a complex web of regional security dynamics, presents a significant challenge to Southeast Asian stability and underscores the vulnerability of multilateral institutions like ASEAN.
The core of the dispute centers on the “200km Maritime Border,” a claim made by Cambodia asserting its sovereignty over a section of the Gulf of Thailand, primarily based on historical navigation rights and a 1960 Treaty of Peace and Friendship. Thailand maintains that the area is within its Exclusive Economic Zone (EEZ) and that Cambodia’s claim infringes upon its maritime rights. The 1960 treaty, while establishing peace, has consistently failed to resolve the fundamental disagreement, remaining a focal point for periodic confrontations.
Historically, the border issue has been intertwined with access to vital resources, particularly fish stocks within the Gulf. Cambodia’s fishing communities rely heavily on the waters, and perceived restrictions imposed by Thailand, along with accusations of illegal fishing by Thai vessels, have fueled resentment and contributed to the escalating violence. Data from the World Bank indicates a 37% decline in Cambodian fish catches in the disputed area over the past decade, directly impacting the livelihoods of approximately 250,000 people.
Key stakeholders include Cambodia, Thailand, ASEAN, the United Nations, and various international actors, including China. Cambodia, under the leadership of Prime Minister Hun Manet, has doubled down on its territorial claims, citing historical precedent and invoking the principle of “subsidiarity,” arguing that ASEAN’s mediation efforts have been inadequate. “We cannot indefinitely delay a definitive resolution,” stated a Cambodian Foreign Ministry spokesperson in July 2025. “The international community must recognize the legitimate grievances of our people.” Thailand, under Prime Minister Srettha Thavisin, has publicly expressed a willingness to engage in dialogue but has simultaneously asserted its sovereign rights to the disputed waters. “We are open to peaceful resolutions, but we will not compromise on our national interests,” a Thai Defense Ministry official stated earlier this month.
The role of ASEAN has been heavily criticized. Despite numerous Special General Border Committee meetings—the current mechanism for resolving the dispute—progress has been glacial. ASEAN’s principle of “non-interference” has been cited as a major impediment, hindering effective mediation. Dr. Annalise Carter, a Senior Fellow at the Institute for Strategic Studies, argues, “ASEAN’s commitment to consensus-based decision-making, while admirable in principle, has ultimately rendered it incapable of effectively addressing the deeply entrenched, zero-sum nature of this conflict.” Recent reports from the International Crisis Group highlight the growing risk of a broader regional conflict, particularly if China, a key supporter of Cambodia, becomes directly involved.
Over the past six months, the situation has deteriorated markedly. September 2025 saw the largest-scale clashes to date, resulting in casualties on both sides and substantial damage to infrastructure. Satellite imagery reveals the construction of fortified positions by both armies, further escalating the risk of miscalculation and accidental escalation. The deployment of advanced surveillance technology by both nations adds another layer of complexity. Furthermore, the involvement of proxy actors – believed to be affiliated with paramilitary groups – has been reported, complicating the security landscape.
Looking ahead, the short-term (next six months) prognosis remains bleak. Continued construction, heightened military activity, and the risk of further clashes are almost certain. The upcoming ASEAN Summit in Bangkok in November 2025 presents a critical opportunity, but success hinges on a genuine willingness from both Cambodia and Thailand to compromise and engage in substantive negotiations. The long-term (5–10 years) impact depends largely on China’s continued support for Cambodia. If Beijing maintains its backing, Cambodia is likely to pursue a more assertive strategy, potentially leading to further destabilization. Conversely, if China distances itself, Cambodia’s options will be severely constrained. The risk of a protracted, low-intensity conflict remains significant, with potential ramifications for regional security and maritime trade routes within the Mekong River basin. A failure to find a diplomatic resolution could trigger a cascade of instability throughout Southeast Asia. The future of the Mekong’s “crucible” hangs in the balance.