Next week, Barack Obama will be the first sitting U.S. president to visit Laos, a poor, landlocked country whose large-scale efforts to dam the Mekong River threaten to destabilize the region. This concerns the United States because Southeast Asia is one of the country’s largest trading partners and a key security ally that can counterbalance China’s growing regional influence. Obama should seize this opportunity to help Laos make energy choices that, over the long term, can unify the region and preserve the Mekong.