Former prime minister Chavalit Yongchaiyudh on Thursday told the National Council for Peace and Order that its time was over and it should hand power to a neutral body to hold elections this year and restore democracy.
Gen Chavalit hosted a news conference at his Bangkok home to publicise an open letter to all "nation-loving" Thais in which he accused the junta of causing conflict and economic hardship.
The former military strongman, known as "Big Jiew", said the NCPO seized power on May 22, 2014 and was able to subdue political conflicts to an extent. But after nearly two years in power, the military government was inciting even more conflict, as well as causing the economy to stagnate, reducing purchasing power and letting exports slump.
"I, as a military officer with seniority, would like the NCPO to ponder this: Since you have already concluded your peacekeeping role, it is now time for you to hand over power to a neutral committee whose members hail from various sectors to administer the country and allow for an election to be held in 2016 and an elected government to be formed," Gen Chavalit wrote in the letter.
Prime minister from 1996 to 1997, Gen Chavalit said the draft constitution prepared by the Constitution Drafting Committee chaired by Meechai Ruchupan had faced growing opposition because its structure and content were undemocratic. Under this new draft, the Thai people would be deprived of sovereign power and the country would be sent backwards for decades.
He said he had learned that the government was trying everything it could to push through the referendum. At the same time, the people had formed networks to reject it.
"From my lifetime experience in solving the country's conflicts, I believe it would be difficult for the NCPO and the government to overcome the problems surrounding them," said the general, who served as supreme military commander from 1987 to 1990.
"In this very complicated situation, without the NCPO's sacrifice of relinquishing power, it will be very difficult for problems to be solved and the burden will fall on people of later generations."
Asked about the possibility of the NCPO staying on for another five years in a "transition" period, Gen Chavalit said he did not see how it would be possible, as the junta came into power only to solve conflicts.
"How could it stay on for five years? Five months is already too long. We have seen what it has done during the past two years. It is even more impossible for it to implement a 20-year national strategy," he said.
"If the NCPO stays on, it would be like some governments in the past which were greeted with flowers on arrival and stoned while leaving."