Sanan Kachornprasart has died at Siriraj Hospital where he was being treated for emphysema for more than two months. He was 78.
Udom Kachintorn, dean of the hospital's faculty of medicine, said the veteran politician suffered from a severe blood infection and died peacefully at 5.09pm on Friday.
Maj Gen Sanan was admitted to the hospital on Nov 22 and had been on a respirator under close monitoring by doctors since then.
The politician from Phichit is survived by his wife, Chawiwan, and four children, including Sririwat, a member of the Chartthaipattana Party.
Maj Gen Sanan was best known as a key figure in pushing for Chuan Leekpai of the Democrats to be prime minister in 1999 by lobbying other parties to join Mr Chuan.
He was rewarded with the post of interior minister until 2000 when the Constitutional Court ruled that Sanan had given false information about his assets and banned him from politics for five years.
He returned to politics after the ban expired before joining Chartthaipattana in 2008 and was a deputy prime minister under the party's quota when the Democrats' Abhisit Vejjajiva was prime minister.
He decided not to take a cabinet position when Chartthaipattana joined the Pheu Thai coalition in 2011.
Maj Gen Sanan was born on Sept 7, 1935 in the northern province. He was chief adviser to Chartthaipattana until he died.
He graduated from the Chulachomklao Royal Military Academy and the United States Army Armour School at Fort Knox.
He was sent to jail for joining Gen Chalad Hiransiri in a failed coup against prime minister Tanin Kraivixien on March 26, 1977. On his release two years later he entered politics, the career he pursued for the rest of his life.