(BangkokPost.com)

The Transportation Federation of Thailand claimed on Wednesday that it has idled 120,000 of the nation's 700,000 lorries to protest high fuel prices.

"If we work we lose money, so it's better not to work," said Thongu Kongkhan, secretary-general of the union.

Fleet and private operators have demanded that the government help solve the rising cost of fuel.

They threatened to drive trucks into midtown Bangkok next Tuesday if "the problem" is not solved.

Prices of all main fuel types passed 40 baht per litre on Tuesday as pump operators responded to the rising cost of oil on the world market.

Trucks were parked along the shoulders 10 kilometres back from the Bang Na entrance to the Bangkok expressway system. Lorries lined the sides of other major highways in Chon Buri, Rayong and Nakorn Sawan provinces.

We want the government to provide us diesel at a special price," Thongu told the news agency Deutsche Presse-Agentur, dpa.

"If we don't get the subsidy by June 17, the entire national truck fleet of 700,000 vehicles will go on strike and descend on Bangkok," he warned.

The lorry operators also demand government subsidies for switching their engines over to use natural gas for vehicles, an operation they say can cost 500,000 baht for the big rigs.

The strikers claimed to represent both large and small truck operators. Several successful Thai politicians have made their fortunes in the country's trucking sector, making it a powerful political lobby.