He began to work as an economist
World Bank In Washington, D.C., United States, and later returned to service until receiving the highest position, namely Deputy Secretary-General of the
National Economic and Social Development Board (NESDB). He entered politics by accepting the post of Secretary-General of General
Suchinda Kraprayoon in 1992 and was appointed Deputy Minister of Agriculture and Cooperatives. In the government of
Anand Panyarachun he was re-appointed Minister of Agriculture and Cooperatives again in the government of Anand 1992. Later in 1994, he was appointed executive director of
Bangkok Bank until the year 1995, he was appointed Minister of Industry. In the government of
Banharn Silpa-archa instead of Chaiwat Sinsuwong and the Minister of Finance. In the government of General
Chavalit Yongchaiyudh instead of
Thanong Bidaya. After that, in 1999 he took the position of Executive Chairman of Bangkok Bank. He returned to politics again in the government of General
Surayud Chulanont, taking the position of Deputy Prime Minister and the Minister of Industry and was appointed Acting Minister of Information and Communication Technology (ICT) in place of Sittichai Phokayudom, who resigned from the case of holding more than 5% of the shares since 30 September 2007. Kosit was appointed a senator in 1996. ==Illness and death==