The project was first sketched in a 1999 study funded by the Asian Development Bank, which concluded it was an unattractive investment - marginal on financial viability, heavy on environmental impact. It did not die. In 2007 Cambodia's Ministry of Mines and Energy signed a memorandum of understanding with Vietnam Electricity for a detailed feasibility study, and in January 2011 Vietnam's Ministry of Planning and Investment licensed EVN to put US$816 million into it. EVN then backed out the same year, keeping a nominal 10 percent. On 26 November 2012 the Royal Group of Cambodia signed a construction agreement with Hydrolancang International Energy, a subsidiary of the Chinese state-owned China Huaneng Group. Construction began in 2014 at a cost of roughly US$781.5 million. Five turbines of 80 megawatts each give the plant 400 MW; the first produced power in November 2017, and after forty years of operation the dam passes to the Cambodian government.

Human Rights Watch put the flooded area at roughly 30,000 hectares, mostly forest, including some 5,000 hectares of farmland. Three villages went under: Srekor, Chrob and Sre Srenok. Nearly 5,000 people were relocated, the overwhelming majority of them Indigenous people and members of ethnic minorities - Bunong, Brao, Kuoy, Lao, Jarai, Kreung, Kavet, Tampuan and Kachok among them. These were communities whose rice land, forest and fishing pools sat within walking distance of one another, arranged by generations of use around a particular bend of a particular river. The compensation package offered around five hectares of land at a resettlement site, a pre-built house or US$6,000 to build one, and a single year of cash to cover the fishing income that was about to disappear permanently.

By 2017, when the walls were finished and the flooding began, more than 700 families had accepted the terms. Over 180 refused them. Most of those families moved instead onto smaller pieces of their remaining ancestral land at the edge of the new reservoir and began seeking communal land titles for it; as of March 2021, none of the communities that had refused to resettle had received title. Kbal Romeas became the name most associated with that refusal, and the reasoning villagers gave was practical rather than symbolic. "The soil of our old farmland was much better than the new farmland," one Kbal Romeas resident explained, "because it was close to the river." The resettlement sites were dry. The rivers they had farmed beside were now underneath a lake, or downstream of a wall.

The losses do not stop at the shoreline. At least 38,675 people across more than 86 villages were projected to lose access to the fishery, and researchers estimated that at least 78,000 people living above the dam site would be cut off from migratory fish entirely, since the structure sits astride the route those fish take between the Mekong and its upstream tributaries. A 2012 study in the Proceedings of the National Academy of Sciences projected that this single dam would reduce fish biomass across the whole Mekong system by roughly a tenth. In a country where fish supply somewhere between 60 and 75 percent of the protein people eat, that is not an abstraction. Human Rights Watch valued the plant's annual electricity output at under US$70 million - a figure the organization judged likely smaller than the fisheries income lost across the basin, which is more or less what the Asian Development Bank's consultants had said in 1999.