Thailand on Monday carried out airstrikes against Cambodian military positions, marking the most dangerous escalation since the US–Malaysia-brokered peace plan began to unravel.

The strikes came after a pre-dawn Cambodian assault that killed one Thai soldier and injured at least two others, according to the Thai military.

The Royal Thai Air Force (RTAF) said its jets targeted weapon depots, command centers, and logistical routes near the contested frontier, describing them as “direct threats” amid what it claimed were Cambodian efforts to mobilize heavy weapons and reposition combat units.

Thai Maj. Gen. Winthai Suvaree said the strikes were aimed at Cambodia’s fire-support positions around the Chong An Ma Pass, which allegedly launched artillery and mortar shells at Thailand’s Anupong Base, causing the fatality.

Thailand also accused Cambodia of initiating the hostilities around 3 am, triggering retaliatory air power. Cambodia rejected the allegations, calling Thailand’s claims “false information,” insisting it had not fired back during either of the morning’s assaults and was adhering to all peace agreements.

The Cambodian army, however, issued a separate statement accusing Thai forces of attacking first around 5.04 am, citing “numerous provocative actions” by Thailand in recent days.

Thailand said around 70% of civilians in border towns have now been evacuated, with one civilian death reported during evacuation due to a medical condition.

The clash threatens to collapse the high-profile peace plan presided over by US President Donald Trump and Malaysian Prime Minister Anwar Ibrahim, who jointly oversaw the expanded ceasefire declaration in Kuala Lumpur in October.

The agreement had been touted by Trump as a major diplomatic achievement, following July’s five-day border war that killed dozens and displaced over 200,000 civilians on both sides.

However, the accord began fraying within weeks. Thailand paused implementation after a landmine blast injured several of its soldiers, accusing Cambodia of deliberate provocations. Both sides have since traded accusations of ceasefire violations amid rising militarization along their disputed frontier.

Monday's airstrikes now mark the most intense confrontation since the ceasefire’s signing, raising fears of a renewed border conflict and putting international mediators back on alert.