Benja Louichareon, director-general of the Excise Department, said many people persuaded by the government scheme to buy their first car cannot receive their tax rebate due to delivery delays.
At present, rebate eligibility depends on both buying a car and becoming its legal owner by the end of this year.
The Finance Ministry will seek approval at tomorrow's cabinet meeting for the scheme's extension in a bid to solve this problem.
Last year's massive flooding inundated many auto and auto parts factories, bringing vehicle production to a screeching halt.
Most of the factories resumed production in this year's first quarter.
But Ms Benja said the situation resulted in delivery delays to car buyers, and in turn many ownership transfers cannot be made in time this year.
"None of this is the buyers' fault, and they should not be forced to miss out on this opportunity," she said.
"So we'll ask the cabinet for permission to give them six more months."
Some 86,000 car buyers had requested the benefit by May for a total excise tax rebate of 6.3 billion baht.
Under the first-car buyer scheme, those eligible must never have owned a car, passenger cars must have an engine size no larger than 1,500 cc, and the price must be no higher than 1 million baht.
The maximum tax rebate allowed is 100,000 baht.
Buyers will receive their rebate within one year from the date of ownership transfer.
Ownership must be maintained for at least five years, or else the rebate will have to be returned.
The scheme, which began last September, was designed to boost auto sales by 500,000 vehicles this year.
The government estimates the rebates will cost it 30 billion baht in lost revenue.
The economy seemed to recover rapidly from the flood crisis, and 40,000 orders were taken at at the 33rd Bangkok International Motor Show this past April.
But carmakers have requested the scheme's extension, as parts supply has not yet fully recovered from the disruption.