However, he stopped short of saying the move was a prisoner exchange, saying Mr Veera had received a pardon, which was a regular practice.
As for Cambodia's request that Thailand respond in kind, he said it could be done under the international prisoner transfer treaty based on reciprocity.
Following Mr Veera's release, Cambodian Prime Minister Hun Sen reportedly asked Thailand to release 14 Cambodian prisoners.
"But I don't know whether the Cambodian embassy has sent the list of names of the prisoners they want to be released to the Foreign Ministry," he said.
Kobkiat Kasivivat, a deputy director-general of the Corrections Department, said a preliminary check had shown 13 Cambodians were being detained for investigation in Sa Kaeo, all of whom were suspects of document forgery.
"Since they have not been prosecuted and therefore do not fall under the prisoner transfer conditions, Thailand could comply [with Cambodia's request] by having the police drop the charges and send them back immediately," Mr Kobkiat said.
Mr Veera, who led a nationalist network allied with the People's Alliance for Democracy or the yellow shirt protesters in 2006-10, was arrested with six Thai colleagues at the end of 2010 after crossing the border to publicise claims that frontier areas held by Cambodia actually belonged to Thailand.
Five were given suspended sentences and released, but Mr Veera, the leader, was sentenced to eight years in prison after being found guilty of espionage, illegal entry and trespassing in a military zone. His assistant, who was sentenced to six years, was released in February last year under a mass pardon.