Dozens of Thai schools were closed and nervous Cambodian residents dug bunkers Monday ahead of a UN ruling over ownership of land surrounding an ancient temple which has sparked clashes between the two neighbours.
At least 28 people have been killed in outbreaks of violence since 2011 over who owns a patch of land adjacent to the 900-year-old Preah Vihear temple.
The Hague-based International Court of Justice is due to rule later Monday on the territorial dispute but there are fears the decision will revive nationalist tensions between the countries and could spark renewed clashes.
Tens of thousands of people were displaced in the fighting, leading Cambodia to ask the ICJ for an interpretation of an original 1962 ruling.
Thailand does not dispute Cambodia's ownership of the temple, a UNESCO World Heritage site, but both sides claim an adjacent 4.6-square-kilometre (1.8-square-mile) section of land.
Leaders of the two countries have appealed for calm ahead of the ruling by 17 international judges.
The mood on both sides of Preah Vihear temple was tense early Monday, with tourists still allowed to visit the ancient structure through Cambodia. But journalists were denied access.
Local residents on both sides said they were taking no chances.
"We have already prepared our bunkers in case Thai troops open fire," So Phany, a vendor near Preah Vihear temple, told AFP.
"We are happy that the international community will know clearly that the temple and surrounding land belong to Cambodia," she added, pre-empting the court's decision.
Some local media reports said Cambodia had sent military reinforcements to the area, but army sources declined to comment when asked by AFP.
On the Thai side, some 40 primary schools were closed in one district on the border Monday, according to a provincial education official, Somsak Chobthamdee.
Thai Prime Minister Yingluck Shinawatra vowed Sunday to "consult" with Cambodia after the decision to avoid any conflict.
"On Monday evening after verdict is delivered the government will announce its position," she added in a post on her Facebook page Sunday.
The verdict poses a particular challenge for the Thai government, which is already grappling with mass street demonstrations over a controversial political amnesty bill.
If the ICJ rules against Thailand, the country's opposition is likely to direct public anger towards the government of Yingluck, whose divisive brother Thaksin is close with Cambodia's premier Hun Sen.
Monday's ruling will be broadcast live on Cambodian and Thai television.