[2][3] Somsak was born and raised in Sukhothai Province and later attended Amnuay Silpa School in Bangkok.

He completed a Bachelor of Engineering from King Mongkut's Institute of Technology Ladkrabang and a master's degree in political science (public administration) from Thammasat University.

He served as deputy minister of public health in Suchinda Kraprayoon's cabinet from April to May 1992 (during Black May).

Having switched to Thaksin Shinawatra's Thai Rak Thai Party (TRT), Somsak was elected to the House of Representatives on the TRT party-list in the 2001 general election, while his wife Anongwan Thepsuthin succeeded him as MP for the first constituency of Sukhothai Province.

In Samak's government and that of his successor Somchai Wongsawat, Anongwan Thepsuthin served as Minister of Natural Resources and Environment from February to December 2008.