Beyond diplomacy: Why IHL governs the Thailand – Cambodia conflict

THAILAND’s caretaker Prime Minister Anutin Charnvirakul made a Facebook post last December 14 publicly denying the existence of any formal ceasefire with Cambodia.

This directly contradicted recent statements by United States President Donald Trump claiming that both countries had agreed to halt fighting. “There was no plan or agreement by the Thai government for a ceasefire with our enemy as of 10 p.m. last night,” Anutin, however, said.

Bangkok’s clarification underscores how fragile and politically charged external mediation has become in this conflict. While diplomatic statements may shape public perception, they do not alter the legal reality on the ground.

Regardless of political declarations or informal assurances, both Thailand and Cambodia remain fully bound by their obligations under international humanitarian law (IHL) for as long as hostilities continue.

The fighting stems from long-standing disputes over border demarcation and control of contested territory, including historic temple sites and strategic borderlands.

Tensions escalated in mid-2025, when shootings and skirmishes gave way to artillery fire, rocket strikes, and air operations.

Given the sustained use of force between two sovereign states, the situation arguably constitutes an international armed conflict (IAC) under the Geneva Conventions. This classification is significant: it triggers the full application of the four Geneva Conventions, Additional Protocol I and customary IHL.

Regardless of political declarations or informal assurances, both Thailand and Cambodia remain fully bound by their obligations under international humanitarian law (IHL) for as long as hostilities continue.

Under IHL, questions of who started the conflict are legally irrelevant to the protection of civilians. Even amid accusations of “Cambodian aggression” or cross-border provocation, both parties are equally bound by core principles: distinction, proportionality, military necessity, and precaution in attack.

These rules are not aspirational; they are binding legal obligations designed to limit human suffering during war.

Civilian casualties have mounted rapidly. Reports indicate dozens killed, hundreds wounded, and widespread displacement. Thailand has acknowledged both military and civilian deaths and imposed curfews after rocket strikes reportedly killed villagers. Cambodian authorities, meanwhile, have reported civilian fatalities, including children.

These developments raise serious IHL concerns. Parties to a conflict must, at all times, distinguish between civilians and combatants, and between civilian objects and military objectives.

Indiscriminate attacks, or attacks expected to cause excessive incidental civilian harm relative to the anticipated military advantage, are prohibited.

Civilian deaths become unlawful when they result from violations of distinction, proportionality, or precaution.

Armed attacks near populated areas demands heightened care. Where military objectives are intermingled with civilian life, attackers must verify targets, choose means and methods that minimize harm, and refrain from attacks where civilian damage would be excessive.

Under the Rome Statute, intentionally directing attacks against civilians or launching disproportionate attacks may amount to war crimes. The reported deaths of children intensify scrutiny, as children are protected individuals under IHL.

Beyond the battlefield, the conflict has broader regional implications. The Philippines has urged de-escalation, with Malacañang warning that hostilities among ASEAN members threaten regional stability.

Advisories have been issued for Filipinos near the border, while analysts caution that prolonged fighting strains ASEAN diplomacy and humanitarian coordination.

As fronts shift and mediation efforts continue, the prospects for peace remain uncertain. For neighboring states, the priority is not only to encourage negotiations, but to insist on strict compliance with IHL.

In conflicts between neighboring states, regional stability ultimately depends not just on political compromise, but on the consistent protection of civilians, accountability for violations, and respect for the legal norms that govern armed conflict.