Residents on both sides of Thailand's and Cambodia's border evacuated in droves on Monday as fresh clashes erupted, killing at least five people.
Both sides have each accused the other of starting the violence, which is the most serious confrontation between the two countries since they agreed to a ceasefire in July.
Thailand's Prime Minister Anutin Charnvirakul says his country never wanted violence but will use necessary means to preserve its sovereignty, while Cambodia's former leader Hun Sen accused Thai invaders of provoking retaliation.
Since May, escalating tensions between the neighbours have led to more than 40 deaths, as well as import bans and travel restrictions.
On Monday, the Thai army said its troops had responded to Cambodian fire in Thailand's Ubon Ratchathani Province, including by launching air strikes along the disputed border; while Phnom Penh's defence ministry said it was the Thai forces that attacked first, in Cambodia's Preah Vihear province.
At least one Thai soldier and four Cambodian civilians have been killed, and about a dozen wounded as a result of Monday's fighting, according to officials on either side.
For Thai teacher Siksaka Pongsuwan, though, there are other, hidden victims of the clashes: the children living near the border, he warns, are losing opportunities and... precious time compared to their peers living in relatively peaceful cities.
Nearly 650 schools across five Thai provinces have been ordered to shut for safety reasons, Thailand's education minister said, following the fresh tensions that have simmered since Sunday.
Meanwhile, videos on social media show chaotic scenes at schools in Cambodia's border provinces as parents rushed to take their children home.
The century-old border dispute between the Southeast Asian nations dramatically escalated with a Cambodian rocket barrage into Thailand on the morning of 24 July, followed by Thai air strikes.
Days later, Bangkok and Phnom Penh agreed to an immediate and unconditional ceasefire brokered by Malaysian Prime Minister Anwar Ibrahim.
In October, both sides signed a ceasefire agreement during a ceremony with US President Donald Trump in Malaysia. At the time, Trump claimed a historic achievement in ending the border conflict.
But just two weeks after that signing, Thailand said it would suspend the implementation of the agreement, after two of its soldiers were injured in a landmine explosion near the Cambodian border.
