Restaurateurs have asked Prime Minister Srettha Thavisin to end the ban on alcohol sales in the afternoon because visitors are complaining.

Sorathep Rojpotjanaruch, head of the Restaurant Business Club, sent an open letter to the prime minister to ask the government to end the ban on sales of alcohol every day between 2pm and 5pm.

According to the letter, the three-hour law has been in place since 1972 and is problematic for restaurant staff because foreign customers frequently ask them to explain why they can't order a drink during the afternoon.

The restriction is outdated, Mr Sorathep wrote, and revoking it would support the restaurant sector, economic growth and the government's campaigns to increase tourism-related revenue.

The alcohol sales restriction was introduced more than five decades ago – reportedly to stop some government officials from partying and drinking in the afternoon. It was more strictly enforced from 2008.