Answer
Nguyễn Ngọc Thơ served as the first Prime Minister of South Vietnam from November 1963 to late January 1964. He was appointed by the military junta that overthrew President Ngô Đình Diệm in a coup d'état on 1 November 1963. Thơ's government was unstable and he was forced to resign in late January 1964 after a failed military coup attempt.