Scholars studying the carvings of the devatas in Thommanon have concluded that it was built around the time when work on Angkor Wat was begun.
However, there is some disagreement as to the precise date it was built.
Some believe that the distinctive carvings of females, known as devatas, indicate that they were built during the reign of Jayavarman VI (1080–1113 AD), some time at the end of the 11th century.
However, there is greater agreement, especially given the scholarly studies, that it was built by Suryavarman II around the time of Angkor Wat and Beng Mealea from 1113 to 1150 AD.

The Vaishnavite cult was adopted in Cambodia by Jayavarman II and his son Jayavarman III.
Under these rulers, the shaivite cult was subsumed with the Vaishnavite cult in the temples such as the Thommannon, Beng Mealea, Chau Say Tevoda, Banteay Samre, and Angkor Wat.

Thommanon is 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 (EFEO).
French archaeologists restored it and added concrete ceilings.
Scholars studying the carvings of the devatas in Thommanon have concluded that it was built around the time when work on Angkor Wat was begun. However, there is some disagreement as to the precise date it was built. Some believe that the distinctive carvings of females, known as devatas, indicate that they were built during the reign of Jayavarman VI (1080–1113 AD), some time at the end of the 11th century. However, there is greater agreement, especially given the scholarly studies, that it was built by Suryavarman II around the time of Angkor Wat and Beng Mealea from 1113 to 1150 AD.
The Vaishnavite cult was adopted in Cambodia by Jayavarman II and his son Jayavarman III. Under these rulers, the shaivite cult was subsumed with the Vaishnavite cult in the temples such as the Thommannon, Beng Mealea, Chau Say Tevoda, Banteay Samre, and Angkor Wat.
Thommanon is 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 (EFEO). French archaeologists restored it and added concrete ceilings.
Thommanon