The eight were arrested on Aug 23 after taking part in a rally calling for energy reforms at the Victory Monument for violating martial law, which allows authorities to detain them for seven days.
About 8am on Wednesday, officers from the Judge Advocate General's Department took the eight from the CSD to the army club on Vibhavadi Rangsit road, where they were released without being charged.
They promised not to again hold or join in a rally in a public place in violation of martial law.
The eight proceeded to the Energy Ministry to attend a seminar on energy reforms for national reconciliation.
Mr Veera said he would continue to campaign for concrete energy reforms, but would not take to the street in violation of martial law as he did last Saturday.
He and his colleagues were glad to have been invited to participate in the energy reforms seminar and would be glad to join every other similar forum, which should be telecast live so the people could know the facts about the country's energy situation, he said.