Divergent Strategies and Domestic Politics Hinder a Resolution to the Cambodia-Thailand Border Dispute

A border incident occurred on 28 May 2025, when a Thai soldier allegedly opened fire near a disputed area along the Cambodia–Thailand border, resulting in the death of a Cambodian soldier. The incident took place in the Emerald Triangle area, which has been under Cambodian control since 1988. In response, both governments expressed a commitment to de-escalate the tensions through bilateral mechanisms, particularly the Joint Boundary Commission.

However, in a rare display of political consensus at the first Senate–National Assembly Congress on 3–4 June 2025, Prime Minister Hun Manet proposed referring the border dispute with Thailand to the Court of Justice (ICJ). The case concerns four sensitive sites, namely Mom Bei region, Ta Moan Thom Temple, Ta Moan Tauch Temple, and Ta Krabei Temple — areas that have been flashpoints of tension in the past. Cambodia is seeking a legal ruling from the ICJ to determine its sovereignty over these disputed territories.

Two primary factors underpin Hun Manet’s decision to pursue adjudication through the ICJ. First, Cambodia has a long-standing tradition of resorting to international legal mechanisms when bilateral negotiations, particularly with neighbours like Thailand, fail to yield results. This strategy is informed by past successes, notably the ICJ’s rulings in Cambodia’s favour in the Preah Vihear Temple cases in 1962 and 2013. As a smaller state historically vulnerable to encroachment, Cambodia views the ICJ as a credible and peaceful forum to safeguard its sovereignty and territorial integrity. The recent border clash, following tensions near Ta Moan Thom Temple in February 2025 when the Thai army accused Cambodian soldiers of encroaching into the disputed zone and singing the national anthem, has further underscored the urgency of legal recourse. The lack of formal border demarcation precludes buffer zones between Cambodia and Thailand and exacerbates the risk of rapid conflict escalation.

From a legal standpoint, Cambodia possesses a strong historical basis for its claim. Central to this argument is the Franco–Siamese Treaty of 1907, signed between France and then-Siam (now Thailand), under which Siam ceded the provinces of Battambang, Siem Reap, and Sisophon to the French, the colonial power in territories presently within Cambodia. Subsequent border maps drawn in accordance with this treaty place the four disputed areas within Cambodian territory.

A collaborative approach rooted in dialogue and mutual respect could pave the way for improved bilateral ties and greater regional cohesion. A refusal to respect international legal mechanisms may entrench hostilities and pose long-term risks to Southeast Asian stability and integration.

Cambodia relied on the same treaty in its previous legal battles with Thailand over the Preah Vihear Temple. In its 1962 judgment, the ICJ ruled that “the temple is situated in territory under the sovereignty of Cambodia, and that Thailand is under an obligation to withdraw any military or police forces, or other guards or keepers, stationed at the Temple or in its vicinity on Cambodian territory.” In 2013, the ICJ reaffirmed this position when Cambodia sought clarification amid renewed tensions. Given these precedents, Cambodia is optimistic that the ICJ will once more rule in its favour.

Second, from a political perspective, the decision to approach the ICJ offers Hun Manet an opportunity to consolidate domestic unity and strengthen his leadership credentials. Since taking office in August 2023, Hun Manet has yet to achieve a major national milestone. A favourable ICJ ruling could serve as his first significant accomplishment, showcasing his ability to transform an interstate crisis into a unifying national cause and to stand firm against a larger neighbour through legal means. The move has already received broad political backing and reinforced his domestic legitimacy, with 182 out of 187 total parliamentarians and Senators voting in favour, including members of the opposition FUNCIPEC Party.

However, while Cambodia seeks a legal resolution, Thailand has filed a formal protest with  Cambodia, asserting that the dispute should be handled bilaterally through the Joint Boundary Commission. The Thai government has persistently rejected the jurisdiction of the ICJ’s 1962 ruling and signalled that it will not recognise any future judgment favouring Cambodia. If the ICJ again rules in favour of Cambodia and Thailand rejects this ruling, Thailand will likely maintain troops in the disputed areas, rendering the ICJ’s ruling ineffective and perpetuating the tensions. The Thai military’s continual presence in the disputed zones would prolong the conflict and increase the risk of escalation.

Thailand’s reluctance to pursue international adjudication remains unclear. However, given Cambodia’s strong legal case, which is bolstered by the Preah Vihear precedent, Thai officials may fear a likely loss. This outcome could damage the credibility of Prime Minister Paetongtarn Shinawatra’s administration, potentially leading to domestic instability and raising the spectre of a political crisis or even a military coup.

Looking ahead, the outcome of this legal battle will likely shape not only the immediate bilateral relationship between Cambodia and Thailand but also the broader dynamics in Southeast Asia. A ruling in Cambodia’s favour would enhance its international credibility and reaffirm its territorial integrity, while simultaneously strengthening national unity and Hun Manet’s political standing. Conversely, if Thailand rejects the court’s jurisdiction and maintains its military posture, it could undermine regional stability and derail efforts toward peaceful conflict resolution. Ultimately, how both nations choose to respond to the ICJ’s decision will be critical. A collaborative approach rooted in dialogue and mutual respect could pave the way for improved bilateral ties and greater regional cohesion. In contrast, a refusal to respect international legal mechanisms may entrench hostilities and pose long-term risks to Southeast Asian stability and integration.

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