The Trapeang Thmor reservoir or Ang Trapeang Thmor is a large-scale irrigation infrastructure located in the area of Phnom Srok district, Banteay Meanchey province. The large reservoir has its origins in the Angkor period, with its ancient road over the dike which connected Yasodharapura (Angkor’s ancient city located in Siem Reap province) to the Banteay Chhmar temple and other geographical areas of the northeastern plateau of Thailand.

Since its beginning until the civil war in 1970, the reservoir was not yet suitable for irrigation. Seen for its potential to use the existing sources of water and for rice cultivation, Democratic Kampuchea, which came to power in 1975, initiated a project. They aimed to build on its ancient road, which extended from the east to the west, and raise the height of the dam of about 11 kilometers and do additional damming on the eastern side, about 7 kilometers.

The Khmer Rouge wanted to use this reservoir for agriculture, but unfortunately, the project failed as it did not follow proper engineering standards. Many people were recruited and forced to participate in this building project. In the cooperative camp, people were forced into labor and many died of illness, exhaustion, or execution.

According to the Extraordinary Chambers in the Courts of Cambodia, Im Chaem was a former Khmer Rouge cadre who was responsible for overlooking this dam construction and other relevant projects. The ECCC charged her in the case 004/01 for her responsibility in the Ang Trapeang Thmor project; however, the charge was dropped later as the court charged only the senior leaders responsible for crimes during Democratic Kampuchea.

Ang Trapeang Thmor, which can reserve 85 million cubic meters of water, has been renovated many times to serve the large rice fields for at least 35,000 hectares in the eastern side of Banteay Meanchey province. This reservoir was also listed as a biodiversity hub for a rare crane species.