Ramathibodi I was the first king of the kingdom
Ayutthaya (now part of
Thailand), reigning from
1351 to
1369. He was known as
Prince Uthong before he ascended to the throne. A native of
Xieng Hai[?] (
Chiang Rai) he claimed descent from
Khun Borom and propagated
Theravada Buddhism as the state religion.