Complex sentence: Fa Ngum's descendants remained on the throne at Luang Prabang for almost 600 years after his death, maintaining the independence of Lan Xang to the end of the 17th century through a complex network of vassal relations with lesser princes.
Split into simpler sentences: Fa Ngum's descendants remained on the throne for almost 600 years after his death. They maintained the independence of Lan Xang to the end of the 17th century by a complex network of vassal relations with lesser princes.