The Customs Department has threatened to file complaints against any importers, owners of bonded warehouses and customs officials found to be involved in avoiding duty payment on more than 400 supercars.
Luxury car importers found guilty of tax avoidance by a court are subject to a maximum of 10 years in prison or a fine of four times the value of the goods, or both. The penalty has been available since 1926, director-general Somchai Sujjapongse said.
The department will also put their names on a blacklist.
Owners of bonded warehouses who allow luxury cars to be taken out without duty payment must face the same penalty as importers, and the department is considering whether it should shut down their businesses, Mr Somchai said.
For customs officials allegedly involved in duty payment evasion, Mr Somchai has instructed units under the department to gather evidence. He plans to set up a committee to launch a probe.
It is the duty of officials to hunt those who dodge payments or they will face charges of neglecting their duties, he said.
Mr Somchai said an initial estimate found more than 400 luxury cars had not been taxed, but the exact figure was under investigation.
Tax avoidance generally happens when importers remove cars from bonded warehouses, so the department may limit importers to removing them only once.
Supercar importers normally park the cars in bonded warehouses and the vehicles are taxed when they are sold or stored for more than a year.
Importers can request a delay in customs duty payment for one more year.
The department plans to review privileges and facilities including allowing imported luxury cars to be stored at bonded warehouses to stem all loopholes.
Customs expects to spend up to two months on its review.
The department has asked for cooperation from the military and police to make sure supercars with red licence plates have had the correct duty paid.
Even if some supercar owners are unaware of tax avoidance, they must take joint responsibility. The crackdown was ordered recently.