The opposition parties have pledged to fight to scale back the defence budget in the second reading of the 3.2-trillion-baht plan after abstaining from voting on Saturday and allowing the 2020 budget bill to pass its first reading.
Following the vote to conclude the three-day debate, a 64-member panel was appointed to examine the spending plan, setting the scene for a showdown between the government and the opposition.
Of the total, 15 members were drawn from the cabinet and the other 49 represent the government and opposition parties with the Future Forward Party (FFP) naming its leader Thanathorn Juangroongruangkit among its representatives to sit on the budget bill scrutiny panel.
Pheu Thai adviser Lt Gen Paradorn Pattanathabut on Sunday maintained the proposed budget does not reflect the needs of the country and would add to its debts at a difficult time.
He was concerned about the allocation of 233 billion baht to the Defence Ministry, saying defence spending was growing owing to an over-estimation of security risks and threats and the military's expanded role and responsibilities.
With an increase of six billion baht from the 2019 fiscal year, the Defence Ministry is among the top four spenders after the Education Ministry, the Interior Ministry and the Finance Ministry.
Lt Gen Paradorn said his party would propose cuts to defence spending and the diversion of those funds to stimulate investments and the economy and boost education and health care.
Mr Thanathorn said on his Facebook page that the party decided to abstain from the vote because it wanted to propose changes to the spending plan in the second reading.
He said while the size of the budget was acceptable, how the money would be spent posed serious concerns.
The FFP leader said the party would adhere to four principles -- cutting back on operation costs, seeking to decentralise spending, investing more in human resource development, and advocating investments for all.
Mr Thanathorn, who is suspended from performing his duty as MP pending a court ruling on his status, said the party would shoot down the bill in the third reading if it comes up short of what the party expects.
The Senate on Sunday set up a 40-member panel to study the budget bill to give them a head start before the bill was forwarded to the upper House, said deputy Senate speaker Gen Singsuek Singprai.
When the bill passed its third and final reading in the House it would be submitted to the Senate for approval but the senators would only have about 20 days to go through the spending plan, he said.
The bill is expected to reach its third reading in January next year.
Senator Somchai Sawaengkarn said on Sunday the upper House is not allowed to make changes to the spending plan, only to screen it.
The budget bill vote has caused a stir in the FFP, after its MP for Chon Buri, Kawinnart Takee, voted in favour of the bill, against the party's stance.
A total of 251 MPs voted in favour, 234 abstained and no MPs voted against the bill.
Theppitak Malasri, head of the FFP working group in Chon Buri, took to Facebook to criticise the MP and call for his resignation.
"A person has betrayed the party's ideology and commitment to the public. I'm calling for your resignation as an MP. You're a disgrace and broke a promise," he wrote.
It was believed he was referring to Ms Kawinnart. It was also her second time voting against the party's stance.
On Thursday Ms Kawinnart, who represents Chon Buri's Constituency 7, also voted in favour of an executive decree to transfer army units to the royal command. She was among three FFP MPs who accepted the bill.
In a related development, the opposition was given 6.94 out of 10 points -- compared to the government's 5.11-- in the debate, according to Suan Dusit Poll.
In terms of satisfaction, 56.4% of the respondents said they were unhappy with the debate while 43.56% were satisfied with it. The respondents gave the opposition 6.04 out 10, while the government scored 5.1.
The poll was carried out among 436 people to compile their opinions on the debate.