His son, Doithibet Duchanee, said there will be praying ceremonies at Debsirin Temple for seven days.
Thawan died of cancer which spread to several parts of the body. He received treatment at Ramkhamhaeng Hospital, according to Thai News Agency.
His royal funeral bathing rite will be hosted Thursday at Debsirin Temple.
Thawan was appointed a national artist on visual arts in 2001.
The Nation