Heavy rain is forecast to continue in 62 provinces, including Bangkok, on Friday, the Meteorological Department reported on Thursday.
According to the forecast, a monsoon trough is making its way down the lower northern region and the upper Central Plains over the next 24 hours, while a moderate southwesterly monsoon is prevailing over the Andaman Sea, the southern region and the Gulf of Thailand, the department said.
The department issued a warning for people in these regions to brace for heavy rain, possible flash floods and forest run-off, especially in lowlands and areas along foothills and near waterways.
The weather agency predicted heavy rain in 80% of Greater Bangkok between 5pm on Thursday and 5pm on Friday, with gusty winds in some areas and the average temperature ranging from 21 to 33 degrees Celsius.
Thunderstorms and heavy rain are expected in 60% of the North, 70% of the Northeast, 70% of the Central Plains, 80% of the eastern region, 60% of the southeastern region and 70% of the southwestern region.
Strong winds are expected to whip up waves of up to two metres in the Andaman Sea and the Gulf of Thailand.