He was the Secretary-General of the State Enterprise Labour Relations Confederation (SELRC), a union of government owned enterprises' employees, and in this position very active in organizing a campaign against the privatization of the Electricity Generating Authority of Thailand.

Kosaisuuk was one of the five leaders of the People's Alliance for Democracy (PAD).

According to a poll conducted by Angus Reid Public Opinion during September 2010, Kosaisuuk was named the least liked politician in Thailand.

[2] In protests against the Yingluck Shinawatra government in 2013–14, his cousin Suthin Taratin, one of the People's Democratic Reform Committee (PDRC) allies, was shot dead in front of Sri Iam Temple, Bangkok's Bang Na area.

[3] Prelude Main events Elections Military junta People's Alliance for Democracy (PAD) National United Front of Democracy Against Dictatorship (UDD)