The reduction in the excise tax on diesel took effect on Friday, resulting in the pump price falling by two baht per litre.
Government House announced that the Royal Gazette on Thursday published the new rate of excise tax on diesel, which would run until May 20.
The rate is temporarily reduced by three baht per litre, in accordance with the cabinet's resolution early this week to ease the impact of high energy prices on the cost of transport and consumer goods.
The tax cut took effect on Friday, when the retail diesel price dropped by two baht per litre to 27.94 baht a litre in Bangkok and its vicinity.
The Energy Ministry collected the remaining one baht per litre to add to the state Oil Fund, which could therefore continue to subsidise oil prices until May 31, instead of March 31, Government House said.
The tax reduction follows a long-running campaign by truckers for a reduction in the cost of fuel. They want the diesel price lowered to 25 baht a litre.