Normally bustling Sai Lom Joy market, on the border with Myanmar in Chiang Rai's Mae Sai district, was shuttered and under water on Tuesday, flooded by overflow from the rain-swollen Sai River.
The river broke its banks on Monday night after heavy rain had pounded the border region since Sunday night, the public relations office in Chiang Rai reported.
The river rose rapidly as anxious traders closed their shops and moved their merchandise to safety, it said. The water was still up to one metre deep in some riverside locations on Tuesday.
The Provincial Electricity Authority has stopped supplying power to users in some flooded areas, worried for their safety. It said about 300 customers would be without electricity until the floodwater subsides.
Sai Lom Joy is a busy, major market on the border between Mai Sai and Tachilek in Myanmar.
District officials were still assessing the damage from the flooding.
The Northern Meteorological Centre on Tuesday warned of more rain, sometimes heavy, in the northern region until next Monday.