The Meteorological Department issued a warning Tuesday to people in 34 provinces in the North, Northeast and East to brace for heavy rain and stay tuned for weather updates.
Flooding in Wellgrow Industrial Estate in Chachoengsao on Tuesday (video by Wichan Charoenkiatpakul)
As of early Wednesday, tropical storm "Rai" was over Laos and the Northeast early Wednesday. The storm was dissipating but dumping tonnes of rain throughout that region.
The tropical depression -- when a low pressure area is accompanied by thunderstorms -- was moving west to northwest at 20kph when it reached Da Nang on Monday night before moving toward the Northeast of Thailand Tuesday evening.
Heavy rain is likely to occur in many of the provinces in the North, Northeast and the Central Plains, extending as far as Sakon Nakhon, Nakhon Phanom, Nakhon Ratchasima, Chon Buri and Chiang Mai.
The Disaster Prevention and Mitigation Department has placed its offices in the 34 provinces on standby, with rapid mobile units ready to be deployed to trouble spots.
In Chaiyaphum, about three hours of continuous rain fell late on Monday night, flooding the provincial town's business district.
The road running past the provincial hospital and Chao Pho Phaya Lae statue was 20-30 centimetres underwater and largely impassable.
The Chaiyaphum municipality used pumps to drain water out into public waterways.
Steady rain was reported in much of Buri Ram throughout Monday afternoon.
Chatchai Promlert, director-general of the Department of Disaster Prevention and Mitigation, said the department has assigned its branch offices in the 28 provinces to stay on alert for possible flooding and landslides.
Flash floods were reported Tuesday in Mae Chaem, Galyani Vadhana and Mae On districts of Chiang Mai province.