The Transport Ministry is calling on owners of illegal luxury motorcycles and cars to register their vehicles before a new ministerial regulation takes effect to avoid legal action.
Deputy Transport Minister Chatchart Sithipan said about 10,000 "big bikes" and 2,000 luxury cars on the streets are not registered.
The new directive is set to ban registration of vehicles assembled locally from imported used body parts. Registration of big bikes and luxury cars will not be permitted under the new regulation.
He said the regulation is expected to take effect this year.
Under the registration process, besides custom tax payments, vehicle inspection and verification is required by the Thai Industrial Standards Institute (Tisi).
"I'm afraid that big bikes may face problems," he said. "Tisi has limited capacity to inspect vehicles. It can do about 16 vehicles a day."
The ministry plans to hold a meeting with big bike operators to discuss the matter on Aug 1.
According to Mr Chatchart, the proposed rule imposes a fine of 2,000 baht. It applies to four types of vehicles - personal vehicles (7 passengers maximum), personal vans, pickup trucks and big bikes.
It is being drafted in line with the cabinet resolution issued last December to tackle tax evasion after it emerged consumers were switching to cars assembled from used imported parts to avoid taxes. The practice is believed to have caused up to 8-9 billion baht in damage to the state.
Meanwhile, Mr Chatchart said the ministry expects to test-run its single ticketing for mass transit systems early next year.
The Office of Transport and Traffic Policy and Planning has been developing a ticketing system which will cover public buses, subway trains and expressway systems.
These three systems are under the jurisdiction of agencies attached to the Transport Ministry.
He said the system is likely to be fully operational in 2014.