The conditions are a result of the strengthening southwest monsoon prevailing across the country, while a low-pressure cell over Vietnam is expected to move through Thailand to the Gulf of Martaban, Myanmar.
People should beware of severe conditions that may cause flash flooding and take precautions during storms.
The department also forecast high waves of 2-3 metres in the upper Andaman Sea due to strong winds and thundershowers. It advised small boats in the area to stay ashore from Saturday to Tuesday, and stay tuned to weather updates.
The affected areas are as follows:
Saturday
Northeast: Nakhon Ratchasima, Buriram, Surin, Sisaket and Ubon Ratchathani.
East: Sa Kaeo, Chanthaburi and Trat
South: Ranong, Phang Nga, Phuket, Krabi, Trang and Satun.
Sunday
North: Tak, Kamphaeng Phet, Phichit, Phitsanulok and Phetchabun.
Northeast: Sakon Nakhon, Nakhon Phanom, Mukdahan, Chaiyaphum, Khon Kaen, Kalasin, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Nakhon Ratchasima, Buriram, Surin, Sisaket and Ubon Ratchathani.
Central: Nakhon Sawan, Uthai Thani, Chainat, Kanchanaburi, Ratchaburi, Suphan Buri, Lop Buri, Saraburi, Sing Buri, Ang Thong, Phra Nakhon Si Ayutthaya, Samut Songkhram, Samut Sakhon, Nakhon Pathom, Bangkok and its vicinity.
East: Nakhon Nayok, Prachinburi, Sa Kaeo, Chachoengsao, Chonburi, Rayong, Chanthaburi and Trat
South: Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Ranong, Phang Nga, Phuket, Krabi, Trang and Satun.
Monday-Tuesday
North: Tak, Sukhothai, Kamphaeng Phet, Phichit, Phitsanulok and Phetchabun.
Northeast: Chaiyaphum and Nakhon Ratchasima.
Central: Nakhon Sawan, Uthai Thani, Chainat, Kanchanaburi, Ratchaburi, Suphan Buri, Lop Buri, Saraburi, Sing Buri, Ang Thong, Phra Nakhon Si Ayutthaya, Samut Songkhram, Samut Sakhon, Nakhon Pathom, Bangkok and its vicinity.
East: Nakhon Nayok, Prachinburi, Sa Kaeo, Chachoengsao, Chonburi, Rayong, Chanthaburi and Trat
South: Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Ranong, Phang Nga, Phuket, Krabi, Trang and Satun.