The central bank’s move came after it received a lot of complaints from banking customers about the practice.
It is common for bank staff to persuade customers to buy financial products, such as insurance policies, when they were accessing another banking service.
Staff often do not disclose enough information for clients to make a sound decision in relation to the service offered.
The central bank’s punishment for offending lenders includes fines and a credit rating cut.
The BOT has also demanded bank executives revamp their employees’ key performance indicators to improve services.