Shopping malls and restaurants in shopping centres are among the businesses that will be allowed to reopen on Sunday, and curfew hours will be shortened by one hour to 11pm.
The decision by the government was confirmed by an announcement published on Friday evening in the Royal Gazette.
Convention centres, wholesale markets and swimming pools will also be allowed to reopen, said Taweesilp Visanuyothin, spokesman for the Centre for Covid-19 Situation Administration (CCSA).
Shopping centres will have to close at 8pm, to give people sufficient time to return home in time for the night curfew.
The state of emergency is still in effect until May 31 but the curfew will start at 11pm, instead of 10pm, and will run until 4am starting on Sunday.
Dr Taweesilp said cinemas, amusement parks, boxing stadiums and gymnasiums would remain closed, while fitness centres would be allowed to resume some activities.
The easing of restrictions comes after regular reports of fewer new coronavirus cases and deaths. There were seven new cases reported on Friday, all people returning from visits to Pakistan, with no new deaths. On Wednesday, there were no new infections at all.
The CCSA spokesman said airports remain closed to commercial flights from overseas, and no alcoholic beverages are allowed to be consumed in restaurants.