The UN's highest court is due to rule on a disputed area of land surrounding the Preah Vihear temple on the border between Cambodia and Thailand.
The long-standing rift has previously led to clashes between the two nations, who both lay claim to the land.
A 1962 verdict by the International Court of Justice declared the temple to be Cambodian, but did not rule on the area around it.
Cambodia sought a clarification of the ruling in 2011, after fighting erupted.
The violence in April of that year left 18 people dead and tens of thousands of people displaced.
Both sides agreed to withdraw troops from the disputed area in December 2011.
On Saturday, the chief of Cambodia's military forces on the Thailand border called an emergency meeting after Thai aircraft were seen flying low around disputed land near the temple.
However, Cambodian regional commander General Srey Deuk told the BBC he expected no problems with the Thai military after Monday's verdict.
He said no troop reinforcements had been brought up to the temple.
But fears remain about possible violence in border villages, stirred up by nationalist groups.
One Thai nationalist group, the Thai Patriotic Network, has said it will reject any judgement from the ICJ, according to The Nation newspaper. The group has already petitioned the court to throw out the case.
The territory has been a point of contention for over a century.
The decision to award the temple to Cambodia in 1962 rankled Thailand, but the issue lay largely moribund due to Cambodia's civil war, which only ended in the 1990s.
It came to the forefront again when Cambodia applied for Unesco World Heritage status in 2008, which it won - angering Thai nationalists. Both sides began a build up of troops in the area.
The ICJ ruling is an interpretation of the 1962 judgement and cannot be appealed.