The heavy rain earlier forecast for the upper northeastern region eased off on Friday as storm Kompasu lost strength over Vietnam and was downgraded to a low-pressure system.
The Meteorological Department said on Friday the storm had weakened overnight as it moved through central Vietnam.
The upper Isan region, especially Mukdahan, Nakhon Phanom, Sakon Nakhon and Bueng Kan, had been warned to expect major downpours when the storm made landfall in Vietnam on Thursday afternoon.
However, the department said isolated rain was still forecast for many parts of the country over the next 24 hours, mainly due to the seasonal monsoon.
Kompasu, Japanese for compass, was the second powerful storm forecast to bring heavy rain to the country, after Lionrock, this month, before it was downgraded.
Lionrock caused serious damage in a dozen provinces and widespread flooding as major dams discharged water from Oct 8 onwards to make room for the runoff generated by the storm.
The Disaster Prevention and Mitigation Department on Friday placed downstream provinces along the Mun River, from Buri Ram to Ubon Ratchathani, on flood alert as a huge volume of water flowed into waterways in the area on its way to the Mekong River.
Kruewan Lasiriyom, resident of Ban Khok Klong in Satuk district of Buri Ram, said her village was already flooded by water from the Mun. She was worried that if the water level continued to rise she would have to leave her home for a safer place.
Prime Minister Prayut Chan-o-cha was visiting Ubon Ratchathani on Friday to inspect flood preparations in the province.
For Bangkok and its neighbouring provinces, the Meteorological Department forecast rainfall over at least half of the capital this weekend, with a chance it could ease off from Monday.
A downpour during the evening rush hours on Thursday in Ngam Wong Wan area caused a traffic jam on the expressway, stretching back at least 10 kilometres after a section of Ngam Wong Wan Road in Nonthaburi was heavily flooded. The flood-hit traffic blocked expressway exits, Radio Jor Sor 100 and Traffic Police networks reported.