Fugitive red-shirt Wuthipong "Kotee" Kochathamakun claims he is training "civilian warriors" to oust the military government.
"We are training civilian warriors to chase the bandits out of the country ... we are training like soldiers," Mr Wuthipong said in an interview on the US-based Thais Voice programme, aired on YouTube on Thursday.
Mr Wuthipong, who fled from Thailand in 2014 after being charged with defaming the monarchy and is believed to be in Laos, said he was training civilian volunteers.
"We are training to protect our brothers and sisters who are for democracy ... I have only just set up the organisation for three, almost four months," he said, adding that the group was based "in the forest", without giving details.
He acknowledged he had few followers. "Not many people have joined," he said.
Defence Ministry spokesman Kongcheep Tantrawanit, dismissed Mr Wuthipong’s talk of mobilising resistance.
"I don't believe anyone would think of destroying their own country," Mr Kongcheep told Reuters, adding that opinion polls showed people were happy with military rule.
Mr Wuthipong is already a wanted man. The government has accused him amassing weapons and of plotting to assassinate the prime minister -- accusations he has denied.
The army chief suggested Mr Wuthipong could have been behind the explosion at Phramongkutklao Hospital in Bangkok on Monday that wounded 25 people. Mr Wuthipong denied involvement in the bombing.
Laos has not made any public comment about him. Requests for his extradition have been ignored.