He graduated from Chulachomklao Royal Military Academy and United States Army Armor School, at Fort Knox, Kentucky.

Afterwards he served as an officer in the tank force (in Thailand traditionally "cavalry") of the Royal Thai Army until he was dismissed for supporting the coup d'état of 26 March 1977, led by General Chalard Hiransiri against the Thanin Kraivichien government.

Sanan, by that time a lieutenant colonel, was imprisoned in Lat Yao prison charged with treason, just like his academy and Fort Knox mate Manoonkrit Roopkachorn.

[6][7] When, after two years of opposition, the Democrats regained government in 1997, Premier Chuan re-appointed Sanan Minister of Interior for a second term until 2000.

The National Anti-Corruption Commission (NACC) initiated investigations on the hint by an opposition MP, that a 45 million baht loan by A.A.S.

On 15 December 2008 the CTP joined the Democrat-led coalition government under Abhisit and Sanan was appointed Deputy Prime Minister with focus on social policies.