Oct 25, 2018 · The eleventh longest river in the world, and one of the longest in all of Asia, the Mekong is certainly the most important in ex Indochina. The famous river starts in Tibet and, after crossing more than 4,000 kilometers through six countries – China, Myanmar, Thailand, Laos, Cambodia and Vietnam, it empties into the South China Sea.. The Mekong is called "Cuu Long Ciang" by the ...