The Senate on Monday night voted to maintain the government's version of Section 3 of the two-trillion-baht borrowing bill.
The section states the government is not required to specify the projects that will be funded by the loan.
The Senate spent over 10 hours debating the bill in its second reading yesterday and managed to pass only three sections of the 18-sections bill. The debate for the remaining sections will resume today.
A Senate ad-hoc committee scrutinising the bill wanted a clause added to Section 3 to make sure the borrowed money would be used to fund the projects listed in the annex of the bill only.
"The change is necessary to prevent misuse of funds, while it still gives some flexibility," said Thawat Bowornwanichayakoon, chairman of the ad-hoc panel.
Chula Sukmanop, a minority committee member, argued the proposed change would require all the listed projects to be implemented. He said that based on feasibility studies, some schemes might not materialise.
Mr Chula is the director-general of the Transport Ministry's Office of Transport and Traffic Policy and Planning.
Sixty-three senators approved the original version of the section, while 52 voted in support of the version amended by the ad-hoc committee. One senator abstained.
Sections 1 and 2 passed their votes earlier as a formality, as they contained no contentious content.
Following the vote on Section 3, the meeting was adjourned at 8.30pm. The Senate will meet today and start deliberating Section 4 of the bill.
Deputy opposition leader Korn Chatikavanij said the Democrat Party will ask the Constitution Court to rule on the constitutionality of the borrowing bill as soon as it passes the Senate's deliberation.
Mr Korn claims this scale of borrowing, which falls outside the normal budget scope, is unlawful.
Appointed senator Paiboon Nititawan yesterday said the Group of 40 Senators will seek the court's ruling if the government's version of Section 6 is also approved.
The Group of 40 has sought changes to Sections 3 and 6.
The Senate committee changed Section 6 to make it clear the loans must be disbursed through the normal budget process instead of a special process written in the government's version.
Mr Paiboon said he also proposed a new section to the bill to allow a group of 10 people to ask the Administrative Court to rule on the legality of the bill.
Meanwhile, Transport Minister Chadchart Sittipunt said his ministry will press ahead with the projects despite the bill being delayed.
Mr Chadchart, speaking at an economic forum held by the Economic Reporters Association yesterday, said about 100 billion baht from the 2-trillion-baht infrastructure plan will be allocated next year.
He said these funds will be spent expanding and repairing Phetkasem and Vibhavadi Rangsit Roads as well as developing dual-track railways between Bangkok and Phitsanulok.
The government will also press ahead with environmental impact assessments of the projects during the court's deliberation, Mr Chadchart said.