"When you have absolute power, it has to be easier" to deregulate energy prices, said Mr Piyasvasti, 61, who was appointed energy minister after a military coup in 2006 and was asked to lead the state oil company's board after the army again seized power May 22. "If it's not done at this time, it will be first coup d'etat that we do not see price reform."
Since ousting Yingluck Shinawatra's government, the junta has made payments to more than 800,000 rice farmers and accelerated budget spending to revive an economy that contracted in the first quarter. Dismantling subsidies would help the military government, known as the National Council for Peace and Order, fund a 2.4 trillion baht plan to modernize Thailand's transport system, Mr Piyasvasti said.
"The junta government appears more able to move quickly on what would be more politically sensitive reforms under an elected government," Chua Hak Bin, a Singapore-based economist at Bank of America Merrill Lynch, said yesterday by e-mail.
Thailand imports about 85% of its crude oil consumption, according to data from the energy ministry. It subsidizes prices of diesel, ethanol-blended gasoline and liquefied petroleum gas through a state oil fund that levies taxes on fuel users.
The junta's economic chief, Air Chief Marshal Prajin Juntong, said May 30 that prices should move in line with the market, raising speculation that subsidies may be removed.
"We need to come to an understanding so we can solve the problem sustainably," Gen Prayuth Chan-Ocha, head of the NCPO, said on June 6, referring to a review of energy prices that's yet to be completed.
The junta may succeed where the democratically elected administration ousted in the coup and the previous appointed government of Abhisit Vejjajiva failed, Mr Piyasvasti said.
Ms Yingluck faced more than six months of protests from groups opposed to the political dominance of parties linked to her brother Thaksin Shinawatra, which have had a lock on electoral majorities since 2001 with a platform of expanded public services and aid to lower-income households. Mr Thaksin was toppled by a military coup in 2006.
"The distortion came back again around 2005 when Thaksin was prime minister," Mr Piyasvasti said. "Everything was deregulated again after the coup d'etat and then distortions came back again when Abhisit became prime minister, to be followed by even more distortion under Yingluck."
Mr Piyasvasti said 95-octane gasoline costs about 48 baht per litre in Thailand, compared with an equivalent price for natural gas for vehicles of 12.7 baht per litre. Removing that distortion will depend on the junta's ability to convince consumers that Thailand isn't "the Saudi Arabia of the east," he said.
"Energy-price rationalization is usually a negative for political capital, especially when an elected government needs to seek a fresh mandate," said Bernard Aw, a research analyst at Forecast Pte in Singapore. "The NCPO will have freer reins to restructure energy prices without fearing it will not perform well in the next general elections."
The junta this week approved the budget for the fiscal year starting Oct 1, which includes 450 billion baht of spending on projects such as a dual-track train network and an extension of Bangkok's mass-transit system. The junta has said it will complete a review this month of its eight-year, 2.4 trillion-baht infrastructure plan.
The central bank in June raised its forecast for economic growth next year to 5.5%, citing an expected increase in government spending and a recovery in confidence. It cut its gross domestic product estimate for this year to 1.5% because of weakness in the first half, before the May 22 coup.
Fuel subsidies remain a challenge for neighbouring Southeast Asian economies including Indonesia, where the two candidates in this month's disputed presidential election pledged to cut fuel subsidies gradually and outgoing leader Susilo Bambang Yudhoyono delayed a plan to raise fuel prices after protests in 2012.
Indonesia's fuel-subsidy bill amounted to about 3.4% of GDP in 2013, compared with 2.9% in Malaysia and 1.4 percent in Thailand, Bank of America's Mr Chua wrote in a report last month.
"While the extent of subsidy is certainly different, we can take some lessons from Indonesia, where years of fuel subsidy have led to the current problems the economy is facing," Gundy Cahyadi, a Singapore-based economist at DBS Group Holdings Ltd, said by e-mail. "This subsidy will be difficult to withdraw in the future, given the kind of political sensitivity it has."
Energy subsidies have cost Thailand an estimated 500 billion baht in the past three years, according to Mr Piyasvasti, similar to the burden of the previous government's rice subsidy program, which the army cited among reasons for the coup.
Mr Piyasvasti, who joined PTT as chairman on July 4, has played a key role in deregulating the energy industry once before. As head of the Thai National Energy Policy Office and energy minister in the 1990s, he led efforts to end oil price subsidies and repay debt incurred by the state oil fund.
He left politics in 2009 to lead Thai Airways International Pcl, where he oversaw a fleet modernization and cost cuts that helped the state-owned carrier rebound from its largest ever loss the year before to a record profit in 2010. The airline slipped to another loss in 2011 as fuel expenses jumped.
Mr Piyasvati was fired in 2012 after Thai Airways said communication difficulties were hampering efforts to meet profit goals, a decision he said at the time could have come from "the top of the political spectrum."
Then-premier Ms Yingluck said the decision was made by the company's board, while Anik Amranand, Mr Piyasvasti's wife and a member of parliament in the opposition Democrat Party, told the Bangkok Post the move was politically motivated. Both Thai Airways and PTT are 51 percent-owned by the Ministry of Finance.
In meetings since the coup, Mr Piyasvasti said he's urged members of the junta to consider boosting tax revenue in favour of taking on more state debt to fund infrastructure projects.
"You can't go on implementing mega-projects simply through borrowing," he said. "What PTT can do is try to educate the general public on pricing reform, but eventually it will have to be the government's decision."