Burma's state-run media New Light of Myanmar reports Thursday that construction of the dam - Ta Sang hydroelectric power plant, the first and largest of four projects on the river, began on March 30th.
Thailand's Thai MDX Group has invested six billion dollars in the joint venture project, which is expected to be completed in 15 years.
The 2800 kilometer Salween River stretches from Tibet in the north, through Burma and along the Thai-Burmese border to spill into the Andaman Sea.
Activists have been calling for a delay of the project, and warn that it could displace tens of thousands of people in Burma and Thailand.
Environmentalists say it threatens the river's ecosystem and endangered wildlife.
Information for this report is provided by AP and AFP