Pruek Prueksunan, a red-shirt activist better known as Yim Tasawang, flashed an anti-coup three-finger salute to reporters as he entered the Army Club on Thewes Road to report to the military junta on Tuesday morning, reports said.
Mr Pruek was one of the 27 individuals summoned by the military's National Council for Peace and Order (NCPO) to report to junta officials in Bangkok between 10am and noon.
Mr Pruek holds up the three-finger salute to reporters as he's about to enter the Army Club on Tuesday, June, 3, 2014.
The reports said Mr Pruek was smiling and waving at reporters outside the Army Club before suddenly giving the three-finger salute.
NCPO spokesman Winthai Suwaree warned on Monday that the military would first consider the intention of those holding up three fingers — a gesture from the "Hunger Games" movies used as an anti-coup symbol - before deciding what action should be taken.
Those showing defiance in a peaceful manner would be held for seven days and released, he said.
Most of those summoned on Tuesday were core members of the Pheu Thai Party and the red-shirt United Front for Democracy against Dictatorship (UDD), such as Prachathai news website chief Thewarit Maneechai and Chulalongkorn University lecturer and member of the Campaign Committee for the Amendment of Section 112 (lese majeste law) Suthachai Yimprasert.
On Monday, red-shirt supporter Sarawut Phuthornyothin committed suicide at his home in Ubon Ratchathani. Sarawut had been summoned to report to the NCPO. His relatives told police they believed Sarawut took his own life because of illness and financial problems, and that his death had nothing to do with being summoned by the junta.