BANGKOK (Bloomberg) - Thailand's junta leader should "salvage" what he can from a flawed draft Constitution and be realistic about what he can achieve during his remaining time in power, former Prime Minister Abhisit Vejjajiva said.

General Prayuth Chan-o-cha must strengthen mechanisms within the charter for political accountability and put it to a nationwide referendum, Mr Abhisit said in an April 2 interview in Bangkok. Most reforms will need to wait until after an election that Gen Prayuth has said could come next year, he said.

Mr Abhisit said he was concerned about the direction of the next Constitution, the first draft of which is due to be released on April 17. The drafters have made it clear they plan to limit the power of politicians. "They've misdiagnosed the problems," said Mr Abhisit, 50, the head of the Democrat party who led Thailand from 2008 to 2011. "They think that the abuses in the past have been due to political parties or politicians being strong. That's not the case."

The problem wasn't the political system, rather the abuses of politicians once they were in power, he said. "They should be making parties stronger but governments more accountable, but they are now making parties weaker but governments less accountable," he said. "For me that's going down the wrong track."

"There are some genuine issues that need to be addressed - inequalities, outdated laws, the gap between the rural and urban people," said Mr Abhisit, 50, the head of the Democrat party who led Thailand from 2008 to 2011. "But all of those for me can be resolved through normal channels, through the democratic process, and what's right, what's wrong, can be resolved through the courts."

Gen Prayuth, then army chief, seized power in May last year after months of protests by both supporters and opponents of former premier Thaksin Shinawatra, who was ousted in a 2006 coup, saying a decade of unrest had divided the country and risked civil war. As prime minister, he has appointed a military-dominated legislature to pass laws, a Constitution-drafting committee to devise a new political system and a reform council to suggest broad changes to society.

While tackling issues as small as rented umbrellas on public beaches, Gen Prayuth has also pledged to bridge the nation's differences, and to do so before elections which he has said could be held in early 2016 if there's no dissent. Critics say Gen Prayuth's policies seek to erase Thaksin's influence and weaken political parties, risking sending the country into further turmoil.

The unrest and military rule has taken a toll on the economy, with consumer prices falling for a third-straight month in March and consumer confidence dropping to a nine-month low after the central bank cut its projections for growth. Manufacturing output rose in February for the first time in 23 months.

"If things were going really well, then maybe the idea of hanging on - you might get away with I don't know how many months," Mr Abhisit said. "But the economy is not good. People are more and more frustrated by the economy.

"They thought that they could go through with austerity type or some structural changes that are unpopular when they started off," he said of the junta. "But given the state of the economy that's going to be too bitter a pill to ask the country to swallow."

Gen Prayuth will have the final say on what reforms are implemented and what the Constitution will look like, having granted himself absolute power in an interim charter drafted after the coup.

He displayed those powers last week by lifting martial law after 10 months and replacing it with similar restrictions on speech and assembly.

The junta has yet to say whether it will let Thais vote on the next charter, something Mr Abhisit said was needed for legitimacy.

"Without it my concern is what if political parties, politicians, and various groups and the people don't accept parts or even the whole Constitution?" he said.

"It would be a great loss of opportunity and time if we are still arguing about the constitution two, three years from now."

Mr Abhisit's party, which hasn't won a national election in two decades, boycotted a vote in February last year amid protests by his allies aimed at ousting then Prime Minister Yingluck Shinawatra, Thaksin's sister.

Mr Abhisit later floated a reform plan that was rejected by both Yingluck and her opponents, that would have required the government to resign and polls to be delayed several months.

The Democrats and Mr Abhisit, who secured the premiership in a parliamentary vote after a Thaksin-backed ruling party was disbanded in a 2008 court ruling, draw their support from southern Thailand as well as Bangkok's upper and middle classes. Support for the Shinawatras comes from the poorer yet more populous north and north-east, and has powered their allies to victory in every national poll since 2001.

Mr Abhisit said the junta was missing political will for reform, in part because politicians had been left out, and as it had set conditions in which proper participation was impossible.

"It's hardly a recipe for success," Mr Abhisit said. "I never had real expectations they could deliver on a number of reforms."

Mr Abhisit denied that his party supported last year's coup. Still, he said the responsibility for preventing future military takeovers also rested with politicians, who should not abuse their power.

"I'm not condoning the coup," he said. "I'm just being practical in saying if you don't want any more coups, let's all help not create conditions for them."

Mr Abhisit has been charged with malfeasance for allowing the use of military force in a crackdown on anti-government protesters - supporters of the Shinawatras - in 2010 that saw more than 90 people killed. He faces impeachment proceedings in the legislature and a five-year political ban if found guilty.

"My job is to prove my innocence," said Mr Abhisit, who points to armed elements within the protest group to defend his government's response. "And I will do it."

For Gen Prayuth, he needs to resist the temptation to stay in power too long, Mr Abhisit said. "He must know that if he outstays the pledge that he has given through his road-map, how can he succeed?"

Gen Prayuth and the junta also must accept that national reconciliation cannot be forced and political differences are a part of democracy, he said.

"There is no way they can force it on the people, there is no way they can force it on the next government, and there's no way that they can stay forever," Mr Abhisit said.

"That's the most important factor that he has to take into account as he moves forward with limited time left."