12th coup since 1932. That makes one every 6.83333333333333333333 years. At least it's something you can count on.
Thailand
June 24, 1932: The Khana Ratsadon party overthrows the absolute monarchy of King Prajadhipok (see Siamese revolution of 1932)
June 20, 1933: Phraya Phahon Phonphayuhasena overthrows Phraya Manopakorn Nititada (see Siamese coup d'état of 1933)
November 7, 1947: Phin Choonhavan overthrows Thawal Thamrong Navaswadhi (see Siamese coup d'état of 1947)
November 29, 1951: Military overthrows 1949 constitution and reverts to 1932 constitution (see Silent Coup (Thailand))
September 21, 1957: Sarit Thanarat overthrows Plaek Pibulsongkram
October 20, 1958: Self-coup of Sarit Thanarat
November 18, 1971: Self-coup of Thanom Kittikachorn
October 6, 1976: Sangad Chaloryu overthrows Seni Pramoj
October 20, 1977: Kriangsak Chomanan overthrows Tanin Kraivixien
February 24, 1991: Sunthorn Kongsompong overthrows Chatichai Choonhavan
September 19, 2006: Sonthi Boonyaratglin overthrows Thaksin Shinawatra