The Meteorological Department on Saturday night issued a warning for people in all regions but the North to prepare for widespread scattered rain with heavy falls in some areas over the next few days.
Deputy director-general Somchai Baimuang said tropical storm Gaemi, now over Vietnam, would pass through Cambodia and Thailand toward the Andaman Sea.
It will trigger heavy downpours in Buri Ram, Surin, Nakhon Ratchasima, Phetchabun, Prachin Buri, Sa Kaeo, Nakhon Nayok, Chon Buri, Rayong, Chanthaburi, Trat, Nakhon Sawan, Uthai Thani, Chainat, Lop Buri, Saraburi, Suphan Buri, Singburi, Angthong, Ayutthaya, Nakhon Pathom, Samut Sakhon, Samut Songkhram, Bangkok and nearby provinces on Sunday and Monday, he said.
The storm could also cause heavy rain in the southern provinces of Prachuap Khiri Khan, Chumphon, Ranong and Phang Nga, Mr Somchai said.