UDD secretary-general and former deputy commerce minister Nattawut Saikuar, Weng Tojirakan, Tida Thawornseth, Veerakant Musikapong and Korkaew Pikulthong left the Army Auditorium at Thewes in vehicles on Wednesday at 4.50pm.
Mr Jatuporn, the UDD chairman, Mr Nattawut, Mr Weng, Ms Tida and Mr Veerakant were taken into the military custody at the army auditorium when army chief Prayuth Chan-ocha declared a coup on Thursday.
Mr Korkaew was arrested by the military at the UDD rally site on Utthayan road in Thawe Watthana district on the same day.
Mr Korkaew was seen lowering a window of his car to wave and smile to reporters as he left.
Mr Nattawut exited the army's premises in his car with his wife and child. He also slowed the vehicle, lowered the window and waved to reporters.
Mr Jatuporn left via a side gate of the auditorium.
Red-shirt activists Nisit Sinthuprai and Kwanchai Praipana, an Udon Thani red-shirt leader, were also said to have been released.
Former deputy prime minister Pracha Promnok and former deputy commerce minister Chaiya Sasomsap, who reported to the NCPO Wednesday morning, have also been freed.
There were no reports whether other former ministers detained by the NCPO had also been released.
Sources said the release of the UDD leaders followed a gentlemen's agreement between them and the army to help Gen Prayuth Chon-ocha, the NCPO leader, set up a tambon-level reconciliation council in every army region with the participation of people representing all political colour codes.