Thailand’s sudden return to use of force along its border with Cambodia is a stark reminder of how volatile one of Southeast Asia’s most protracted territorial disputes remains. The pace of recent escalation is alarming. Just a few weeks ago, leaders from both countries stood before regional and international dignitaries at the Association of Southeast Asian Nations (ASEAN) summit to endorse a ceasefire framework presented as a political breakthrough. The symbolism was heavy, and the ceasefire, celebrated by regional leaders and witnessed by US President Donald Trump, was meant to demonstrate that Southeast Asia can responsibly manage its own tensions.
However, that promise quickly disappeared once the delegation returned home. Bangkok’s airstrikes on Cambodian military positions in the disputed border area caused immediate evacuations.
What this sequence reveals is painfully familiar. A ceasefire in this conflict is unlikely to amount to more than a pause in a long cycle of distrust. Although agreements are signed in conference halls, the frontier itself has its own rhythm, shaped by long-standing grievances, conflicting domestic narratives, and the difficulties of managing heavily armed forces operating in ambiguous terrain.
The ceasefire approved at the ASEAN Summit was built as the basis for a broader roadmap. It promised both sides to cease hostilities, halt troop movements and gradually reduce the deployment of heavy weapons near disputed areas. Importantly, it ordered ASEAN to deploy a monitoring team to monitor compliance.
On paper, these were smart steps. In reality, they were grafted onto a political soil that was far from ready to sustain them. Both governments, operating under intense global scrutiny, were keen to demonstrate calm to foreign investors, but core issues such as unresolved borders, unresolved historical claims and mutual suspicion embedded in their security systems remained untouched.
As such, the agreement functioned less as a resolution and more as a temporary gesture of goodwill to avoid international pressure. Its weaknesses quickly became apparent. The agreement relied more on the momentum generated by the summit itself than on durable institutional mechanisms. High-profile witnesses can create a sense of ceremonial grandeur, but they are no substitute for the hard work needed to rebuild strategic trust.
Thailand and Cambodia entered into the agreement with different interpretations of what compliance means, particularly regarding military posture and patrol rights in disputed areas.
More importantly, the proposed surveillance regime called for close real-time cooperation between two militaries that have long viewed each other through adversarial lenses. Surveillance missions can only be successful if field commanders respect their access, accept the consequences, and operate under harmonized rules of engagement. Those conditions don’t exist yet.
And domestic political considerations are at play in all of this. In both Bangkok and Phnom Penh, leaders have become sensitive to accusations of weakness in territorial integrity. In environments where nationalist sentiment is easily stirred up, governments often act defensively and even preemptively to avoid domestic political backlash.
historical grievances
To understand why this conflict keeps returning to the brink, we need to place it within its long arc. The border between Thailand and Cambodia reflects the legacy of colonial demarcation. France, which ruled Cambodia until 1954, was deeply involved in border demarcation, but the process left vague lines and overlapping claims.
These ambiguities mattered little when both countries were preoccupied with domestic integration and the chaos of the Cold War. However, as institutions matured, national narratives became more firmly established, and economic development changed the strategic value of particular regions, border conflicts intensified.
Some of the disputed areas have deep cultural and symbolic significance, such as the Preah Vihear temples built by the Khmer Empire, which both Thailand and Cambodia claim to be its successors. In 1962, the International Court of Justice (ICJ) ruled that the temple was within Cambodian territory.
The conflict erupted between 2008 and 2011, crystallizing political interests and featuring exchanges of fire, mass displacement, and contested legal interpretations of ICJ decisions. The clashes not only damaged property and displaced civilians. They embedded the border issue into the nationalist consciousness of both countries. The years of relative calm that followed were built on a precarious equilibrium.
This year’s resurgence in violence follows that established pattern. Domestic politics in both capitals has entered a phase where leaders feel they must show resolve. Military modernization programs, on the other hand, provide both sides with more means of coercion, even if neither side desires full-scale confrontation.
With troops approaching disputed territory, there is little margin for error. Routine patrols can be mistaken for provocations, and ambiguous movements can quickly escalate into an armed response. In such an environment, ceasefires, however well-intentioned, are unlikely to survive unless supported by mechanisms that address deeper structural issues.
The fact that the ASEAN-brokered ceasefire agreement did not directly address the most disputed areas of the border left ASEAN vulnerable. Neither Thailand nor Cambodia are prepared to accept binding boundaries that could be interpreted as domestic concessions. Until legal, cartographic and political perspectives are clarified, the region will remain one that both sides feel compelled to assert.
External factors require more complex calculations. Both countries operate in a geopolitical environment characterized by great power competition. Although neither Thailand nor Cambodia seeks to internationalize their conflicts, there are competing incentives to project autonomy, avoid external pressure, or demonstrate strategic alignment. Although these dynamics may not lead to direct conflict, they create a political environment in which leaders feel additional pressure to project strength.
What ASEAN should do
The effects of this escalation extend beyond bilateral relations. If airstrikes, even coordinated ones, become a regular means of signaling, Southeast Asia risks entering an era in which a strong position becomes the default position in territorial disputes. The evacuation of civilians is likely to increase further. Confidence-building measures, already fragile, could evaporate completely. And the political space for diplomacy, which depends on leaders having the space to escape extremist rhetoric, could shrink dramatically.
ASEAN is now facing a test of relevance. Symbolic diplomacy, expressions of concern, and offers of “nice greetings” are not enough. If an organization wants to demonstrate that it can manage conflict within its ranks, it must take three important steps.
First, it must insist that the surveillance mission be fully developed and granted operational autonomy. Observers need unrestricted access to flashpoints, and their assessments must be publicly reported to reduce the temptation for either side to distort the facts. Although transparent monitoring does not eliminate conflict, it can reduce opportunities for opportunistic escalation.
Second, ASEAN should establish a permanent trilateral crisis group consisting of Thailand, Cambodia, and the ASEAN chair. This group should be required to intervene diplomatically within hours of an incident being reported. Timely engagement could prevent misunderstandings from escalating into a military response.
Third, ASEAN must begin laying the groundwork for long-term negotiations on border delimitation. This is a politically sensitive issue and there may not be a quick solution, but a structured process supported by neutral cartographers, legal experts and historical researchers could create room for gradual movement. Slow dialogue is better than no dialogue.
The United Nations cannot replace ASEAN leadership, but it could complement it. The United Nations’ technical expertise in border disputes, experience in managing verification processes, and capacity to support humanitarian preparedness could strengthen regional efforts. Importantly, UN involvement has the potential to depoliticize highly technical issues that are often intertwined with nationalist rhetoric.
But all these institutional measures will be meaningless unless political leaders in Bangkok and Phnom Penh are willing to honestly face the past and consider potentially unpopular compromises. Sustainable peace requires more than a respite from violence. It requires voters who are willing to accept that historic differences must be resolved through negotiation rather than force or symbolic posturing.
The recent collapse of the ceasefire should not be seen simply as another unfortunate event, but as a sign that Southeast Asia’s security architecture remains incomplete. Although the region has made remarkable progress in economic integration and building diplomatic habits, structural weaknesses remain when it comes to managing high-stakes territorial disputes. Without meaningful investment in transparency, shared rules, and reliable enforcement mechanisms, even the best-known agreements will remain vulnerable to political winds.
Thailand and Cambodia are currently at a crossroads. They can continue on a path where regular escalations become normalized, or they can choose to participate in a process that will lead to a final resolution, however long and incomplete. The former costs will be borne by civilians, border communities, and regional stability. The benefits of the latter will extend far beyond the realm of commons.
The views expressed in this article are the author’s own and do not necessarily reflect the editorial stance of Al Jazeera.
