The downpour continued until late Friday morning, generating floods that swamped hundreds of houses in Chiang Kham and Pong districts of the northern province.
Chiang Kham district chief Nopparit Sirikosol said the Lao and Yuan rivers overflowed and flooded homes and farmland in four villages in Mae Lao and Rom Yen sub-districts.
Somchart Phuangphayom, chief of the Phu Lanka National Park in Pong district, said 218 millimetres of rain fell on Phu Lanka mountain, the heaviest downpour this year. The runoff was swelling all rivers around the mountain in Chiang Kham and Pong districts.
In Pong district, runoff from the mountain and flooding from Kha and Ngim rivers submerged five villages in Ngim sub-district. About 200 residents were isolated in Moo 11 village.
Kanyanat Srijai, deputy mayor of Ngim municipality, said the floodwaters surged into Moo 11 village about 9am. The water was over two metres deep and reaching the roofs of one-storey houses.
The flooding occurred too fast for locals to move their belongings to safe places. At least 700 houses were inundated in Ngim sub-district alone, Mrs Kanyanat said.