The three had been charged with gathering in a group of more than 10 people and physical assault resulting in public unrest after they participated in a violent protest outside the home of the late Privy Council president Prem Tinsulanonda in 2007.
Weng was thankful for the royal pardon, which came after it was felt he should no longer be detained due to illnesses from being elderly. However, he said he would remain true to his ideology in protesting against the dictatorship.
He said he did not intensively follow political news during his detention but acknowledged the big student protest planned for September 19. He, however, did not intend to participate because of health issues.
Thida Thavornseth, one of the former red-shirt movement leaders, was present at the release and gave each of the three men a hug to celebrate their freedom.
Other red-shirt activists also turned up to show their support and give the three leaders garlands as rain fell to cheer them up.