or Phumiphon Adunlayadet or Rama IX
born Dec. 5, 1927, Cambridge, Mass., U.S.
Ninth king of the Chakri dynasty and Thailand's longest-ruling monarch.
A grandson of King Chulalongkorn , he succeeded to the throne in 1946 after the death of his older brother, King Ananda Mahidol (r. 1935–46). His role as head of state is largely ceremonial, but he moderates between extreme parties in Thai politics and serves as a focus of national unity.