Resurgence of Thai-Cambodian Border Tensions and Lessons from the Region

Amidst ASEAN nations confronting the recent tariff announcements by the US, an escalation of a longstanding border dispute adds to yet another challenge facing the 10-member bloc, raising questions about the effectiveness of the bloc.

Border skirmishes have erupted yet again between Thailand and Cambodia, which saw the death of one Cambodian soldier, border closures, and suspension of Thai Prime Minister Paetongtarn. This recent flare-up of a longstanding dispute—rooted in colonial-era legacies originating from treaties signed between Siam and France as early as 1867—has generated a more pronounced political impact domestically, particularly within Thailand, and reignited nationalist sentiments and escalated militarisation along the border.

The renewed border tensions have triggered significant domestic political fallout in Thailand. Prime Minister Paetongtarn Shinawatra—already facing public dissatisfaction over a weak economy, poor disaster response to the recent 7.7-magnitude earthquake, and broader leadership concerns—has seen her legitimacy decline. A leaked phone call with Cambodia’s former premier Hun Sen, in which she criticised a top Thai military commander as unhelpful and positioned herself as willing to resolve issues bilaterally, greatly tarnished her reputation. Her deferential tone—referring to Hun Sen as “uncle”—and remarks perceived as undermining the Thai military, sovereignty, and dignity sparked public outrage.

Although Paetongtarn later apologised and framed the call as a negotiation tactic, the damage was done. Public outrage persisted, culminating in the Bhumjaithai Party’s withdrawal from the coalition. The party accused her of compromising Thailand’s sovereignty and military dignity. The incident not only eroded public trust but also deepened tensions between her family and the powerful Thai military.

These recent foreign policy missteps, particularly regarding national security, have become a rallying point for opposition protests. Thousands have taken to the streets in Bangkok, with “yellow shirt” protesters once again voicing their discontent. The yellow shirt movement has historically been hostile to the Shinawatra political dynasty and backed by royalists, military and business elites. Their return signals renewed polarisation in Thai politics. Not long after, the Constitutional Court suspended her from office, pending investigation into the controversial phone call.

The May 28 border clash led to a series of retaliatory steps by both countries. Thailand tightened controls at several border checkpoints and imposed stricter immigration protocols. In turn, Cambodia barred Thai workers, cut fuel imports from Thailand, and banned Thai cultural products such as films and TV, as well as suspended internet services. Further economic retaliation included a halt in the import of Thai agricultural goods. These tit-for-tat exchanges have severely affected the livelihoods of border communities due to their inability to engage in cross-border work which greatly disrupts cross-border commerce.

At the root of this border dispute is a lack of political willingness to reach a settlement by both sides on border demarcation as well as differing interpretations of old treaties. The Preah Vihear temple dispute, in particular, has remained contentious. In 1962, the International Court of Justice (ICJ) ruled that the temple belonged to Cambodia. Continued clashes from 2008 to 2011 prompted Cambodia to seek a clarification of the judgment. In 2013, the ICJ reaffirmed Cambodian sovereignty over the temple and surrounding areas, obliging Thailand to withdraw its troops.

However, the current skirmish occurred at a different border area near Ubon Ratchathani, within the Emerald Triangle. Both governments blame each other for instigating the violence and have put both their armed forces on high alert. Thailand asserts its soldiers acted in self-defence after Cambodian troops refused to withdraw and used live fire, while Cambodia maintains its forces were fired upon without provocation.

Despite the existence of the bilateral Thai-Cambodian Joint Boundary Commission (JBC), progress on demarcation and mutual agreement has stalled. Cambodia has expressed willingness to return to the ICJ, but Thailand rejects third-party adjudication, arguing that sensitive matters involving complex historical territorial disputes are better managed bilaterally. Without mutual consent, the ICJ is unable to act and has no jurisdiction, exemplifying the limitations of international legal mechanisms that rely heavily on state consent.

From Myanmar to Thailand and Cambodia, ASEAN’s credibility is again under scrutiny for its capacity to manage regional conflicts. Its norms emphasise peaceful dispute resolution and non-interference, as outlined in the ASEAN Charter. While informal, bilateral diplomacy—often labelled “the ASEAN Way”—is a common practice, its lack of structure and unregulation can backfire, as seen in the leaked call. Despite good intentions, the incident revealed the risks of unregulated diplomacy in protracted, nationalistic disputes, especially when political dynasties are intertwined. Such approaches only work when both parties are genuinely committed to de-escalation or resolution.

In contrast, archipelagic Southeast Asia may offer more examples of effective conflict resolution. The Pedra Branca dispute between Singapore and Malaysia and the Sipadan-Ligitan case between Indonesia and Malaysia were both peacefully resolved through ICJ rulings, facilitated by mutual consent. Both states in these cases accepted the ruling of the court and moved forward in their relations. These cases illustrate the value of political will and legal mechanisms when both parties seek an enduring solution.

Another method of resolving protracted border disputes is through joint development of overlapping claims. Thailand and Malaysia for example, established the Malaysia-Thailand Joint Authority (MTJA) through an agreement in 1979. Instead of engaging in long-term border disputes in the Gulf of Thailand, they opted to share natural resources in their overlapping maritime border claims in a 50:50 manner. As a result, both economies benefit from natural resources exploration as a joint venture instead of bickering over territory. Revenue sharing is viable with sufficient political will and mutual trust. While similar efforts have been explored in the Thailand–Cambodia maritime context, disparities in domestic capacity—particularly Thailand’s more advanced oil and gas sector—may mean any agreement would yield unequal benefits.

A particularly pertinent example involving conflict de-escalation is the 2013 Lahad Datu standoff in Malaysia. The incursion by armed followers of the self-proclaimed Sultan of Sulu from the Philippines resulted in casualties but did not escalate into an inter-state conflict. Despite Manila’s historical claims over Sabah, the Philippines publicly distanced itself from the militant group while then Filipino President Benigno Aquino urged the group to surrender or face full extent of the law. Malaysia treated the event as a counterterrorism operation rather than an act of war, with Malaysia distinguishing between state and non-state actors. Diplomatic channels remained open throughout the crisis, preserving bilateral relations. Neither side wished to escalate.

The Lahad Datu example demonstrates that even incidents with deep historical and territorial implications can be resolved—or at least contained—through calculated response, careful diplomacy, legal framing, and inter-state coordination. It also highlights the importance of separating state actions from non-state provocations. Friendly relations between two disputing states in the examples given could serve as lessons where long-term bilateral relations, mutual trust and peaceful resolution is emphasised over nationalistic posturing or scoring of political points in name of national interest or sovereignty. The Thai-Cambodian case, however, is being complicated by increasing mutual mistrust, entrenched political dynasties and rising nationalist fervours.

Unless there is a renewed commitment to formal dispute resolution—whether bilaterally through the JBC or multilaterally via ASEAN’s good offices—the current trajectory points toward prolonged instability. One hopeful prospect lies in regional leadership: just as Indonesia attempted to play a mediating role during the 2011 Thai-Cambodia border clashes, Malaysia could take a more proactive position under Prime Minister Anwar Ibrahim, who has publicly called for restraint and adherence to ASEAN principles.

The resurgence of tensions between Thailand and Cambodia reflects the fragility of conflict management mechanisms in Southeast Asia when informal diplomacy overshadows institutional resolution – particularly if there is mutual mistrust. Drawing from past examples like the Lahad Datu incident and successful ICJ-mediated settlements, the region must recommit to legal clarity, diplomatic discipline, political will and mutual trust. For ASEAN to maintain its relevance, it must strengthen not only its declaratory principles but also its operational capacities to prevent minor border skirmishes from escalating into prolonged crises.

DISCLAIMER: All views expressed are those of the writer and do not necessarily represent that of IIPA and this platform.

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Author

Hazwan Dani Abdul Kadir is a PhD candidate at the University of Canterbury, New Zealand. His current research focuses on conflict escalation, de-escalation, small state security, and state behaviour and response in asymmetric and conventional conflict environments.

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