Known best for serving during the late 1990s as Prime Minister of Cambodia, this Funcinpec Party politician also held office as Cambodian Minister of Foreign Affairs.
In the early 1990s, he began his political career as Cambodia's Minister of Posts and Telecommunications.
Following his service as prime minister, he established the largely unsuccessful Rastra Niyum political party.
He was raised in Cambodia's Kandal Province and later worked and studied in Melbourne, Australia. He married Ung Malis Yvonne.
He and Hun Sen governed Cambodia as joint prime ministers.