As Thom means big, Prasat Ta Muean Thom is the biggest one in this group of edifices. Located on the Phanom Dong Rak Range, this ruin lies on the route linking the Angkor Wat and Angkor Thom to Prasat Hin Phimai. It is now hidden amidst lush forest, the southern part of which is right on the Cambodian border.

The compound has 3 towers, the principal one in the central and the smaller one on its left and right, made from pink sandstones.

Two laterite wihan exist on the East and West. The compound is surrounded by sandstone cloister. Of the four gopuras, entrance pavilions, the southern one is the biggest and links to the balustrade that drops off to the slope in Cambodia.

A pond lies on the north outside the cloister. A Khmer inscription on the southeastern cloister refers to a person named Phra Kalapa Krisna.

No man-made lingum is found here. A big rock, representing lingum, is found in the principal tower, similar to the one found at Yot Phu Kao in Champasak in southern Laos.