Restaurants are being warned they must clearly advise customers in advance if a service charge will be added to their bill, otherwise diners can refuse to pay the extra.
Nuntawan Sakuntanaga, director-general of the Internal Trade Department, said the service charge, and the rate, should be clearly stated on the menu or announced by a sign at the counter or out in front of the restaurant, so that customers are aware of this additional cost.
The service charge became an issue on social media after a lawyer announced that diners have the right to refuse paying this charge.
Mr Nuntawan said if a restaurants fails to inform a customer in advance but insists on collecting the charge, the consumer can file a complaint via hotline 1569. Officials will be sent to investigate and if the restaurant is found to be at fault it will face a maximum fine of 10,000 baht.
Ms Nuntawan said the department felt the service charge should be around 10%. If they charge more, restaurants may be found guilty of overcharging, which carries a maximum penalty of a 140,000 baht fine and/or a seven year jail term.