Nanthasen[1] (also spelled Nanthasan; Lao: ພຣະເຈົ້ານັນທະເສນ, died 1795), also known as Chao Nan, was the 6th king of the Kingdom of Vientiane.
However, his younger brother Inthavong was crowned the oupahat ("vice king") by Siam, and left in Bangkok as hostage.
In 1791, Nanthasen convinced Rama I that King Anurutha of Luang Prabang was secretly meeting with the Burmese and plotting a rebellion against Siam.
Chỉ devised a plan to unite Vientiane and Muang Phuan in a revolt of Tây Sơn dynasty.
In January 1795, Nanthasen accused of plotting a rebellion[5] with the Lao governor of Nakhon Phanom, allegedly having made diplomatic overtures to Tây Sơn.