1979, after the 'Khmer Rouge' regime was overthrown, he became Foreign Minister in the Vietnamese-installed 'People's Republic of Kampuchea/State of Cambodia'
1985, he was elected Chairman of the 'Council of Minister's and subsequently the Prime Minister
Following the national leader's declaration stating his unwillingness to part with his authority, the 'Cambodian National Rescue Party' along with other protest groups organized peaceful rallies in Phnom Penh
They demanded re-elections because allegedly the July 28, 2013 elections were unfair. The protests garnered the attention of United Nations which condemned Sen's use of power to dissipate the peaceful protestors
2005, 'Sri Chinmoy Centers International' presented him with its highest award, the 'U Thant Peace Award,' for his role in the progression of Cambodia and the entire 'ASEAN' nations