People in the northeastern, central, eastern and southern regions have been warned of more rain from Monday to Saturday.
Although the impact of tropical storm Ma-on has died down, the Meteorological Department on Sunday alerted the four regions to the likelihood of more rain - together with possible flash floods and water runoff - over the next six days.
More than half of the areas comprising Greater Bangkok should brace for rain from Thursday to Saturday, the weather forecasters added.
Ma-on triggered torrential rain in the country from Wednesday, leaving some areas in 11 provinces still under water and drowning a man in Chiang Rai.
Flooded locations were reported in Lampang, Phetchabun, Ubon Ratchathani, Udon Thani, Buri Ram, Khon Kaen, Maha Sarakham, Nakhon Ratchasima, Nakhon Nayok, Ayutthaya and Ang Thong, according to a bulletin on Sunday from the Disaster Prevention and Mitigation Department.