The Meteorological Department (TMD) continued to warn people in several parts of the country to prepare for torrential rain as tropical storm Sonca claws its way toward Vietnam's coast from the South China Sea.
In its announcement issued Tuesday morning, the TMD said the eye of the storm was about 300 kilometres east of Nakhon Phanom in the Northeast and moving at low speed toward Vietnam's coast.
The storm was forecast to reach Hue, a city in central Vietnam, by Tuesday afternoon and then begin losing strength to become a tropical depression by the time it hits Laos, after which it is expected to move closer to the Northeast.
Heavy rain is forecast for all regions in Thailand.
The rain may trigger flash floods and floods caused by water overflowing river banks nationwide, the TMD said.
A strong southwest monsoon over the Andaman Sea and southern Thailand is continuing to whip up strong winds and torrential rain along the west coast of the South, it said.
Waves of up to three metres have been forecast in the region from Tuesday until Saturday, the weather agency said.
Small boats are being warned to refrain from venturing out to sea during this period.
In the Northeast province of Kalasin, at least 2,000 rai of paddy fields in Muang district have been flooded as river banks overflowed after being inundated by water from the Lam Pao dam.
A flash flood causing evacuations was reported in the early hours Tuesday in Phrae.
About 50 families in Ban Pak Pan in tambon Sai Yoi in Den Chai district were forced to evacuate after water in Pak Pan creek suddenly overflowed its banks and flooded their homes, said Col Chakkares Siriphong, commander of the 12th Cavalry Battalion in Den Chai.
He led a team of soldiers to rescue flood victims.
Thongsuk Bankhiew, 58, whose lives by the creek, said she didn't have time to pack her bags before the flood came and she had to flee.
Such heavy flooding has not been seen in recent years, she said, blaming the construction of a weir two years ago.
Although the floodwaters receded later, residents were being advised to stay on high alert.
Meanwhile, the 8th Royal Irrigation Office in Nakhon Ratchasima assured the public that the five dams in the province are capable of receiving more water.
Only three dams were more than half full as of Tuesday.
They were Lam Phra Ploeng dam (57.1% full) in Pak Thong Chai district, Lam Plai Mat dam (58.8%) in Soeng Sang district, and Lam Chae dam (51.4%) in Khon Buri district, said Chitchanok Somprasert, director of the irrigation office.
The other two dams, Lam Ta Khong in Sikhiu district and Lam Mun Bon in Khon Buri district, are 25.6% and 48.8% full, respectively, he said.