The department director-general, Chirut Wisalchit, said on Friday that his agency had told private bus operators to remove the ads from their vehicles within three days of receiving the written notification.
If they fail to do so, the bus operators would be deemed to have displayed advertisements without permission of the department and would be fined 1,000 baht per bus and per sighting.
“We expect the ads to be removed from all private buses within January,” the director-general said.
He explained that the regulation allows bus operators to remove paid ads from their vehicles if the business involved is linked to alleged violation of law.
Kong Salak Plus chief executive Panthawat Nakvisut is being investigated by the Department of Special Investigation for allegedly obtaining money for his business from a money laundering ring.
Investigation by the DSI found that several million baht had been transferred to Kong Salak Plus from a criminal gang allegedly involved in the drug trade, fake call-centre fraud, and online gambling. Many gang members were arrested recently when records of money transfers were discovered. The records reportedly showed a Kong Salak Plus executive as among the recipients of money from the gang, according to police.