Wan Kadir Cheman, a former chief of the Bersatu separatist group, has warned Thailand not to pin its hopes on the Mara Patani group in peace talks because it does not represent all of the groups involved in the southern unrest.
Speaking at the King Prajadhipok's Institute on Friday, Mr Wan Kadir said he knows six of the seven Mara Patani representatives at the peace talks.
The peace talks in Malaysia will not bring an end to the unrest in the deep South because people see the problem from different angles, Mr Wan Kadir said. Peace negotiations with Malaysia serving as the facilitator have been going on for 20 years, he added.
The negotiations have never ended southern violence.
In fact they have made it worse, he said.
"It's no easy task to get the influential people to the negotiating table.
"Those people [at the table now] are also real but they aren't the ones who are really active and they have no influence over the groups in the far South," he said.
Thai authorities should focus their efforts on starting secret peace talks with the influential groups in southern Thailand, he said.
Mr Wan Kadir also said he doubts if Malaysia can actually help Thailand with the peace negotiations.
Even though Malaysia intends to help, he said, the country is seen as an outsider.
Thailand should find a qualified Thai to act as a negotiator, he said.
"We should have tried to resolve the problem in Thailand. Why do we have to cross the Sungai Kolok River to resolve the problem? Does Malaysia know our problems better than we do?" he said.
"Others may not be sincere or even if they are, they may not really understand our problems and cannot resolve them," he said.
"Those who are still active in the southern violence have visited me and told me not to talk too much. They said I have already quit the battlefield and I should be aware of what the punishment for that will be," he said.
Peace talks between Thai authorities and southern insurgents have stalled as the Thai government considers the separatists' requests for immunity from criminal prosecution and for the talks to be made an official part of the Thai national agenda.