Democrat Party leader Abhisit Vejjajiva has hinted he could leave politics for good if his party does not win at the next election.
Mr Abhisit made the remarks during a speech Sunday, entitled "Building inspiration for political careers" to Rangsit University's PhD students in the Philosophy Programme in Leadership in Society, Business and Politics.
"I do not have much time left for political work. I do not know when the election will happen. When the next poll is held, I will contest it. But if I do not succeed, that will be the end," Mr Abhisit said.
"I am a three-time opposition leader, which is more than enough. It would not be right for me to be opposition leader a fourth time."
Mr Abhisit, who turns 51 in August, said he would have ended his political career at the age of 50, if certain political events hadn't occurred. He said he would pursue other interests after his political career ends.
Politics has been unsatisfactory over the past 23 years of his career, but he does not regard his career as a waste of time, he said.
"Although the current political situation is not what we want, we have to keep fighting," the former premier said.
"With the emergence of the National Council for Peace and Order, no matter whether we want it or not, the hope is that we want rule of law and democracy to return in a sustainable manner," Mr Abhisit said.
People want to see the political system take shape as quickly as possible so the process of democracy can ensue, he said.
In the first one or two years, efforts must be made to lay out a good system to reinforce public strength, Mr Abhisit said.
He insisted a referendum on a draft constitution must be held to stay the incessant debate on the charter.
Prime Minister Prayut Chan-o-cha and his government had put forward many good ideas, including reform plans, although he was uncertain whether all the plans would be put into place.