The 24-hour forecast is for heavy isolated downpours across the lower North, Central Region including Greater Bangkok, East, and South.
The department warned people to beware of flash floods, especially along foothills, near waterways and in low-lying areas.
Waves in the upper Gulf of Thailand and Andaman Sea will be 1-2 metres, rising higher in thunderstorms. Ships have been advised to proceed with caution and keep off thundershowers.
The severe weather is being produced by a low-pressure cell in the upper Andaman and a monsoon trough across the upper South.
The department issued separate forecasts for each region.
North:
Northeast:
Central:
East:
South (east coast):
South (west coast):
Greater Bangkok:
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