The Nam Ngum-Dam is the first and largest dam of the Democratic People's Republic of Laos . It dams the Nam Ngum about 90 kilometers north of the Laotian capital Vientiane . The dam was built in 3 stages between 1968 and 1984 and is primarily used for energy supply, with a large part of the electricity being exported to Thailand . The dam is also used for flood control, irrigation and as a tourist destination. The lake can be reached from the capital via national road 13. The hydropower plant is operated by the state-owned Électricité du Laos. The generators have an output of 155 megawatts . The technical facilities were modernized in 2010 with the help of the Japan International Cooperation Agency .