Thai schools closed and nervous Cambodian residents dug bunkers or evacuated homes Monday before a UN ruling on which country owns land surrounding an ancient temple, an issue which has sparked deadly clashes.
At least 28 people have been killed in outbreaks of violence since 2011 over the ownership of a patch of border land next to the 900-year-old Preah Vihear temple.
The Hague-based International Court of Justice (ICJ) is due to rule later Monday on the territorial dispute, but there are fears the decision will revive nationalist tensions and 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) piece of land.
Leaders of the two countries have appealed for calm before 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 via Cambodian territory. 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.
Other villagers along the border with Thailand left their homes altogether fearing the worst, said an AFP photographer at the scene.
"We have to take proactive measures. I will leave my home for a few days, we fear that Thai troops might cause clashes," villager Va Vy, 29, told AFP as he prepared to leave.
The Cambodian army denied local media reports that it had sent military reinforcements to the area.
"The situation along the border is normal," regional military commander, General Srey Doek, told 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.
A local village headman said a number of villagers had left to stay with families.
On her Facebook page Thai Prime Minister Yingluck Shinawatra vowed Sunday to "consult" with Cambodia after the decision to avoid any conflict, adding her government would make a statement following the verdict.
The ruling, which will be broadcast live on television, is fraught with danger for her government, which is already grappling with mass street demonstrations against a controversial political amnesty bill.
If the ICJ rules against Thailand, the country's opposition is likely to direct public anger towards Yingluck, whose divisive brother Thaksin is close to Cambodia's strongman premier Hun Sen.
Cambodia has allowed Thaksin -- who is in self-exile from Thailand to avoid a jail term -- to hold a number of rallies for his "Red Shirt" supporters on its soil.
There are fears a negative verdict for Thailand will increase anger among hardline nationalist elements currently on Bangkok's streets.
Last year the ICJ ruled that both countries should withdraw forces from around the ancient Khmer temple, which is perched on a clifftop in Cambodia but is more easily accessed from the Thai side.
Cambodia and Thailand finally pulled hundreds of soldiers from the disputed zone in July 2012, replacing them with police and security guards.
In a television appeal last week Hun Sen urged his armed forces to "to remain calm and show restraint", adding he had agreed with his Thai counterpart to abide by the ICJ's decision.
The roots of the dispute lie in maps drawn up in 1907 during French colonial rule.