Mekong River In Cambodia is the important river. The Mekong is considered one of the world’s major rivers. It is the 11th-longest river in the world, and the 12th-largest by volume. Its estimated length is 4,880 km. From the Tibetan Plateau, it runs through China's Yunnan province, Burma, Thailand, Laos, Cambodia and Vietnam. The extreme seasonal variations in flow and the presence of rapids and waterfalls have made navigation on the Mekong extremely difficult.