The use of liquefied petroleum gas (LPG) for motor vehicles rose 42 percent year-on-year to 2,461 tonnes in May, and by 5.4 percent from April, according to the Department of Energy Business.

The government fixes the local price of LPG at $333 a tonne, against prevailing global prices of more than $800, making the fuel highly attractive, said Viraphol Jirapraditkul, the department's director-general.

Most Bangkok taxis run on LPG, which until a few years ago was used mainly as cooking gas by households and food vendors.

Mr Viraphol said the LPG refill station business was booming, with 1,020 stations operating as of the end of May, compared with 672 a year earlier. Margins from LPG are relatively attractive as well, at three baht per kilogramme compared with 0.90 to 1.20 baht a litre for oil retail sales.

The department estimates that there are 700,000 LPG-compatible vehicles on the country's roads but some industry sources say the true figure could be closer to one million.

Compressed natural gas or CNG - popularly known locally as NGV or natural gas for vehicles - is also gaining more fans, thanks to a capped price of 8.50 a kilogramme that has been in place for nearly seven years, against a real price of around 13 baht.

CNG consumption rose 42.4 percent year-on-year in May and 10.4 percent from the previous month to 6.24 tonnes per day.

The number of new and converted CNG vehicles entering the market is also rising by 500 units per day from an average of 350 a day in 2010.

"Oil prices may stay above $100 per barrel throughout this year and motorists have been trying to curb the cost of living by shifting to fuel with fixed prices," said Mr Viraphol.

The use of petrol in May dropped 3 percent month-on-month to 19.96 million litres per day, but was up 3.3 percent from May or last year.

Among petrol consumption, ethanol-based petrol rose significantly.

Sales of E20 grew 84.5 percent year-on-year to 622,000 litres per day but dropped 2.9 percent from 641,000 litres a day in April. E85 sales rose fivefold to 23,000 litres per day from a year ago and by 31 percent from 17,000 litres in April.