Thommanon is a small temple built at the end of Suryavarman II's reign, around the middle of the 12th century. It is nearly symmetrical to Chau Say Tevoda, another of Suryavarman's temples that stands nearby.
Thommanon is a single-towered temple with an east-facing central sanctuary, crowned by a prasat, or tower. Access from the east is via a gopura, followed by a mandapa, or antechamber, before arriving at the central sanctuary. The temple's carvings are very well preserved and the aged sandstone provides a distinct contrast to the surrounding jungle. The architectural style of its tower is also akin to the Ankor Wat temple and the Chau Say Tevoda in its vicinity.The independent building separated from the main temple was the library.
Thommanon is located directly opposite the Chau Say Tevoda and just 500 metres east of the Victory Gate on the way to Ta Keo. In the 1960s, the temple underwent a full restoration, funded by the École française d'Extrême-Orient. French archaeologists restored it and added concrete ceilings.