The government's move to divert unspent budgets to the central fund could run afoul of laws, Democrat leader Abhisit Vejjajiva says.
The former prime minister said the current administration has indicated unspent budgets given to state agencies could be drawn into the central fund, which he found to be curious considering such a move is prohibited by law.
"The government must clarify the matter as the Budgetary Procedures Act bans the transfer of budgets across agencies," he said.
Mr Abhisit pointed out the example of the current administration recent indication that it would allocate more money to state welfare cardholders by drawing unspent money from other agencies.
According to him, the central fund is normally set aside for urgent or emergency incidents.
Mr Abhisit said he was surprised by the government's commitment it would give money to local areas they visited during mobile cabinet meetings, saying the administration would not be able to do so if it did not set aside the budgets in advance.
"The only way the government can do so is to use money from the central fund," he noted.
The National Legislative Assembly (NLA) last week endorsed a 3.3-trillion-baht budget for 2019 fiscal year, which starts on Oct 1.
Referring to the government's decision to set a budget deficit at 450 billion baht in 2019, Mr Abhisit said this shows that the government is spending more money than it gets. To fill the gap, it has to seek loans whose burden of repayment will be shouldered by the public, he said.
He noted that Thailand's outstanding public debt of six trillion baht adheres to international standards. However, the government has to continuously monitor whether the total amount actually increases or decreases, he said.
He said several governments have tried to keep the public debt in check by pushing state-run financial institutions to provide financial support.
However, each government has had to seek money to offset the loans, which meant people were liable for it.
"I want to know where public debts are hidden," said Mr Abhisit.
Since the regime took power in 2014, government budgets amounted to 14 trillion baht -- 938 billion baht of which were set aside for the Defence Ministry.