The opposition will petition the Constitutional Court to rule on the legality of the 3.2-trillion-baht budget bill for the fiscal year of 2020, if the government fails to provide expenditure details as required by the constitution.
Chief opposition whip and a Pheu Thai MP for Maha Sarakham, Suthin Khlangsaeng, said on Sunday the opposition has studied the budget bill and found some budget allocations proposed by the government do not meet the requirements stipulated by the constitution because they do not include details on what the money will be used for.
''If the government fails to revise the bill, the opposition will take the matter to court,'' Mr Suthin said.
Political observers noted that if the court accepts the opposition's petition, the promulgation of the bill will be delayed pending a court ruling, which will then affect the running of the country.
Moreover, if the court rules the budget bill violates the constitution, the pressure will shift to Prime Minister Prayut Chan-o-cha, who could decide to dissolve the House or even resign.
Mr Suthin also criticised the budget, saying a significant part will be allocated to security-related ministries, such as the Defence and Interior ministries, while the sums allocated for improving the economy and public welfare schemes -- including the 30-baht universal healthcare card scheme -- are comparatively small.
"The bill also earmarked a lot of money to be held as reserves for emergencies, but no spending details were given," he said.
"The central emergency budget can be allocated to other ministries, so it has to be able to be scrutinised in a transparent manner," Mr Suthin said.
Of the 3.2-trillion-baht budget requested, 74.7% or 2.39 trillion baht will go towards funding the regular budget -- up by 5.3% from 2.2 trillion in the fiscal year of 2019.
In the fiscal year of 2020, the government expects to collect 2.73 trillion baht in revenues, up by 7.1% from 2019.
That said, the government will be running a deficit of about 469 billion baht -- up 4.3% from the previous fiscal year -- which will go towards investments.
The total amount requested for investments for the coming fiscal year is 655 billion baht -- approximately 20.5% of the total budget.
The bill will be tabled before the House of Representatives for its first reading on Thursday, and the House is expected to take between 2-3 days to raise their concerns. The second and third readings are likely to take place in January.
Last week, the cabinet set up a 63-member panel which will vet the bill in its second reading.
The panel will be made up of 15 representatives from the cabinet, 24 from the opposition parties and another 24 from coalition parties.
On a related note, an opinion poll carried out by Suan Dusit Rajabhat University, or the Suan Dusit Poll, found most Thais believe the 3.2-trillion-baht budget requested by the government is "excessive", but will nevertheless pass through parliament with little opposition.
The poll was carried out between Oct 9-12, in which 1,034 people across the country were asked about the opinion on the bill.
When asked if the budget is appropriate, 58.7% of respondents said "no", with the majority saying that the amount is high, which makes it prone to misuse and may cause the country to fall further into debt.
Meanwhile, the 41.3% of respondents who said "yes" to the same question said that the budget is appropriate because the money is needed to further develop the country and stimulate the economy.
A large majority -- 70.4% -- believed the bill would get parliamentary approval.
Only 29.62% said it would fail to get approval, with most saying that the proposed expenditures do not justify the amount requested, while others cited the slim majority the government commands in the House as a possible hurdle.