Representatives of taxi drivers rallied at the Transport Ministry on Tuesday, demanding 8.5 billion baht in compensation from the government if the GrabTaxi service is legalised -- and threatening to sue the prime minister and the transport minister if they didn't get it.

Leading the rally of his Association of Public Taxi Motorists, Worapol Kaemkhunthod said taxi drivers opposed all forms of ride hailing services, including GrabTaxi, because they took advantage of conventional taxi drivers.

"A Grab driver's costs are about 8,000 baht but a taxi driver's are over 25,000 baht per year. Aside from that, taxi drivers have to pay 20,000 baht for the Taxi OK application," Mr Worapol said, The Land Transport Department launched the Taxi OK app for taxi drivers.

"If ride hailing services are liberalised, we deserve compensation estimated at 8.5 billion baht," he said, basing the figure on the cost of the Taxi OK app and the number of taxi drivers.

Liberalised ride hailing services would make taxi drivers uncompetitive and crime would rise, Mr Worapol said.

If GrabTaxi is legalised, he said, his association would file a complaint with the Administrative Court against the prime minister, the transport minister and concerned transport officials for malfeasance causing damage to taxi drivers.