Kraisak Choonhavan, a well-known academic and politician, died at 72.
The only son of Gen Chatichai Choohavan, Thailand's 17th prime minister (1988-91), and Khunying Boonruen, Kraisak was well-known for his role as a negotiator who helped turn Indochina "from a war zone to trade zone", a key policy of his father's government.
Kraisak held a bachelor's degree on foreign relations from the George Washington University and a master's degree from the School of Oriental and African Studies in England.
After finishing his studies, he taught at Kasetsart University in Bangkok before joining his father's government as an adviser.
He represented the Thai government at meetings to solve disputes in Cambodia and at peace talks in Cambodia, Laos and Vietnam.
After his father's government was toppled by a coup led by Gen Sunthorn Kongsompong in 1991, the family went abroad. A year later, Kraisak returned and joined the 1992 uprising.
He was elected senator for Nakhon Ratchasima in 2000 and chaired the Senate's committee on foreign affairs.
He joined the Democrat Party and was elected deputy party leader. He became a party-list MP in the 2007 election before the Prime Minister Abhisit Vejjajiva dissolved the House in 2011.
A BBC Thai interview in August described him as “one of the people closest to and most affected by military coups”.
He was born in 1947, the year his grandfather, Field Marshal Pin Choonhavan, staged a coup. When his grandfather’s adversaries staged a coup 10 years later, his parent took him to Argentina. His father’s government was also toppled by a putsch in 1991 when he was serving as an adviser.
Before the 2006 coup, Kraisak was one of those who heavily criticised former prime minister Thaksin Shinawatra and spoke on a stage of the People's Democratic Reform Committee. However, he backed down when the protests urged the military to stage a coup.
After the latest coup in 2014, Kraisak heavily criticised the Prayut Chan-o-cha government on curbs on freedom of expression and policies that affected the environment and communities.
Kraisak was diagnosed with base of tongue cancer in 2015 and died on Thursday at Siriraj Hospital.