The site is in a northwestern region of Cambodia's border with Thailand, 543km from the Phnom Penh, the Cambodian capital.
The temple is several hundred kilometres west of 11th century Preah Vihear temple, where Cambodian and Thai soldiers have been locked in a standoff for three weeks in a dispute over land near the temple.
Tharit Charungvat, the Thai foreign ministry spokesman, said Thai soldiers were deployed in an 80m radius around the temple ground and have prevented Cambodian troops from entering.
At least 40 Cambodian soldiers are in close proximity to the Thai troops, he said.
Although it is not as well known as the Angkor or Preah Vihear temples, Ta Moan Thom is one of the architectural wonders of the ancient Khmer empire.
It was built in the 13th century as a rest house along a road linking the ancient Angkor city with what is currently northeastern Thailand, Chuch Phoeun, a Cambodian ministry of culture official, said.
The border dispute erupted last month near the Preah Vihear when the United Nations Educational, Scientific and Cultural Organisation (Unesco) approved Cambodia's application to have the complex named a World Heritage Site.
Samak Sundaravej, the Thai prime minister, had backed the bid, sparking anti-government demonstrations near the temple.
At least 800 troops from Cambodia and 400 from Thailand remain at a pagoda near the temple complex, despite a tentative agreement reached by foreign ministers last Monday to redeploy them in an effort to ease tensions.