Somsak began his political career as a Member of Parliament representing Khon Kaen.

In 1997, at the time a member of the New Aspiration Party, he was Vice Speaker of the House of Representatives.

During this time, he acquired the nickname "The Hammer Man" ("ขุนค้อน") for his impartiality in presiding over the House's meetings and intensive use of the presidium's gavel.

[1] Later, he was a member of the Thai Rak Thai Party of Prime Minister Thaksin Shinawatra, which was banned after the 2006 coup d'etat, and transferred into the People's Power Party (PPP).

Somsak who exercised restraint during the 2010 Thai political protests, is considered to be also acceptable for the parliamentary opposition.