The Land Transport Department found that 405 out of 10,056 taxis in Bangkok violated the law in October, the department chief said on Saturday.
Pirapol Thawornsuppacharoen, director general of the department, said 84 of the 405 taxi drivers rejected their customers while 69 refused to use meters. The rest committed other offences.
The department also found that 41 of 6,149 passenger vans broke the law during the same period for failing to install safety equipment for passengers.
The department also found that 13 taxi motorcyclists violated the law for failing to register their motorbikes as public transport vehicles.
All the offenders have been filed and sent for attitude-adjustment sessions, Pirapol added.