According to the Thai Meteorological Department's 14th storm warning notice at 5am, although "Hato" located in upper Laos had been downgraded at around 4am, much of the country would face more rainfall.
The rain is coming from the southwest monsoon currently prevailing over the Andaman Sea and Thailand.
The affected provinces would include Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Lampang, Phrae, Nan, Uttaradit, Phetchabun, Loei, Udon Thani, Nong Khai, Bung Kan, Sakon Nakhon, Nakhon Phanom, Mukdahan, Amnat Charoen, Ubon Ratchathani, Si Sa Ket, Chon Buri, Chanthaburi, Trat, Ranong and Phangnga.
Residents in those areas should prepare for flash floods and closely follow weather advisories, the department said.