[2] Kosit was born and raised in Bang Lamphu oldest town in Bangkok.

He completed secondary education from Saint Gabriel's College and he graduated with a bachelor's degree in finance (honors) from the Faculty of Political Science, Chulalongkorn University.

[3] 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.

[5] He died of cancer on 1 June 2016[6] at King Chulalongkorn Memorial Hospital aged 73.