Heavy rain is expected in about 50 provinces in all regions until Friday, with flood and landslide warnings current, and could continue in the lower part of the country until Monday.
Chayapol Thitisak, director-general of the Department of Disaster Prevention and Mitigation, said on Wednesday people living in low-lying areas along the Chao Phraya River and its tributaries should move their belongings to high ground.
Heavy rain, with possible flooding and landslides, was forecast for 15 provinces of the North - Chiang Mai, Chiang Rai, Kamphaeng Phet, Lampang, Lamphun, Mae Hong Son, Nan, Phayao, Phetchabun, Phichit, Phitsanulok, Phrae, Sukhothai, Tak and Uttaradit.
The same weather is forecast for the 13 northeastern provinces of Amnat Charoen, Buri Ram, Chaiyaphum, Kalasin, Khon Kaen, Loei, Maha Sarakham, Nakhon Ratchasima, Roi Et, Si Sa Ket, Surin, Ubon Ratchathani and Yasothon.
The warning also applies to designated provinces in the Central Plain - Ang Thong, Ayutthaya, Chai Nat, Kanchanaburi, Lop Buri, Nakhon Sawan, Ratchaburi, Sara Buri, Sing Buri, Suphan Buri, Uthai Thani - and to greater Bangkok.
Included in the warning were eight eastern provinces - Chachoengsao, Chanthaburi, Chon Buri, Nakhon Nayok, Prachin Buri, Rayong, Sa Kaeo and Trat.
In the South, 10 provinces can expect more rain - Chumphon, Prachuap Khiri Khan, Krabi, Phetchaburi, Ranong, Phangnga, Phuket, Satun, Surat Than and Trang.
The Meteorological Department stated on Wednesday that from Saturday to Monday rain would decline in the North, the upper Northeast and the upper Central Plain but would continue in the lower Central Plain including the greater Bangkok, the lower Northeast, the East and the South.