Later, Sanan entered politics. He became a member of the Democrat Party. From 1988 until his leave in 2000, he held the position of Secretary-General of the party. He served as Minister of Agriculture from 1988 to 1990 and Deputy Prime Minister for three months in autumn 1990 under Chatichai Choonhavan, as Minister of Industry from 1992 to 1994 and as Interior Minister from 1994 to 1995 in Chuan Leekpai's first government, notable for forbidding the police to pursue lèse-majesté cases. 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. He was Chuan's Deputy Prime Minister from 1998 to 2000. In 2000 Sanan came under the suspicion of corruption. The National Anti-Corruption Commission initiated investigations on the hint by an opposition MP, that a 45 million baht loan by A.A.S. Autoservice, in fact was no loan. On 23 August the Constitutional Court ruled that Sanan had given false information about his assets and banned him from politics for five years in accordance with article 295 of the 1997 Constitution. After his ban expired, Sanan left the Democrat Party. In 2004 he founded the Mahachon Party, together with Anek Laothamatas. Sanan served as the secretary of the party. The Mahachon Party won 8.3% of the votes and two of the 500 seats in the 2005 election. In 2007 Sanan and his son Siriwat left the party for the conservative-populist Thai Nation Party, coalition partner of the People's Power Party in the Somchai Wongsawat government. In early-December 2008, the Constitutional Court dissolved all governing parties, the Nation Party was mostly reborn as the Thai Nation Development Party, of which Sanan is the chief adviser. 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. After the 2011 election, he resigned from the cabinet, even though the CTP was also part of the new Pheu Thai Party-led coalition. Sanan Kachornprasart died in Bangkok on 15 February 2013 at the age of 77.
Private life
Sanan was married to Chawiwan Kachornprasart and they had four children. His third son is also a CTP politician, Siriwat Kachornprasart, who was deputy minister of commerce in Yingluck Shinawatra's cabinet. Sanan owned the biggest ostrich farm in Thailand, called "Kajorn Farm" and a vineyard in Dong Charoen District, Phichit Province, where he cultivated the wine "Chateau de Shala One".
Honours
Royal decorations
Sanan has received the following royal decorations in the Honours System of Thailand:
