Three bodies were found drowned in floodwaters in Nakornsawan province, 240 kilometres north of Bangkok, the Department of Disaster Prevention and Mitigation said in its latest flood report.
The inundation has affected more than 68,000 households nationwide.
In Nakornsawan alone, over 27,000 households are submerged and approximately 384 square kilometres of farmland are damaged.
Ayutthaya province in central Thailand saw a number of historical sites and temples reportedly submerged in water half a metre deep.
More than 22,000 households are flooded in Ayutthaya, while a total of 13 provinces are declared flood disaster areas, officials said.
Bangkok City Hall on Friday also issued a flood alert for parts of the city.
- DPA