"The Indonesian government and the people of Indonesia expressed deep condolences over the death of Thanat Khoman," the foreign ministry noted a statement received here Saturday.
"Our prayers and sympathies go to his family, friends and colleagues hoping they will be given strength," it noted.
Thanat Khoman was foreign minister of Thailand from 1959 to 1971 and deputy prime minister from 1980 to 1982.
He helped strengthen the relations between his country and the United States during the Vietnam war.
Khoman died at the Ramathibodi hospital on Friday of old age.
He was a leader who had contributed and given invaluable service to promoting regional reconciliation and cooperation in Southeast Asia.
He was one of the founders of ASEAN along with the late Indonesian former foreign minister Adam Malik, former Philippine foreign minister Narsisco Ramos, Malaysias former foreign minister Tun Abdul Razak and Singapores former foreign minister S. Rajaratnam.
With his death ASEAN no longer has "founding fathers" that would personally see various developments and achievements of ASEAN cooperation in the future.