Xe Bang Fai RiverThe Xe Bang Fai River is a river in Laos. It originates in the Annamite Range on the border between Laos and Vietnam at. It flows through Khammouane Province and Savannakhet Province.Xe Bang Fai River CaveXe Bang Fai River Cave is in Hin Namno National Park in Khammouane Province. It is believed to be one of the largest river caves in the world with passages some 120 meters tall and 200 meters wide, and a subterranean channel seven kilometres long.