People living in Prachuap Khiri Khan and Phetchaburi have been warned about possible flash floods on Monday and Tuesday.
According to the Thai Meteorological Department (TMD), a strong southeast monsoon will bring heavy rain over the Andaman Sea and the Gulf of Thailand.
This may cause water levels to rise, which in turn could cause rivers to overflow, the Disaster Prevention and Mitigation Department warned.
“The rather strong southwest monsoon prevails over the Andaman Sea, the South and the Gulf of Thailand”, the warning read.
The TMD said the wind will cause waves of more than 2 metres high in the upper Gulf of Thailand.
All ships were advised to proceed with caution and avoid going out at sea during thunderstorms.
Residents, particularly those living in areas prone to flooding, should monitor the weather forecasts.
In addition to Prachuap Khiri Khan and Phetchaburi, the flash flood warning was issued for a 21 other provinces, including Bangkok, Samut Sakhon, Samut Songkhram, Samut Prakan, Chachoengsao, Chonburi, Rayong, Chanthaburi, Trat, Chumphon, Surat Thani, Nakhon Si Thammarat, Songkhla, Pattani, Narathiwat, Ranong, Phang Nga, Phuket, Krabi, Trang and Satun.