Floodwater still persists in 18 provinces while more rain is expected later this week and early next week, authorities said on Tuesday.
Bangkok, Nonthaburi, and Pathum Thani were also put on alert from the rising Chao Phraya River.
The Disaster Prevention and Mitigation (DDPM) said the flooding, mostly in the central region, had now spread to 32 provinces and 7,489 villages with 286,577 affected households since tropical storm Tien Mou passed through Thailand on September 23.
Eight people have died and one person is missing.
They said the situation has improved in 14 provinces but there is still flood water in 18 provinces.
The Thai Meteorological Department expects more rain throughout the country from a tropical depression between October 5 and 9.
The tropical storm Lionrock is also expected to pass through Nakhon Phanom which will lead to heavy rain in the province, Bueng Kan and Udon Thani between October 11 and 12.
The DDPM now warned of floods in 24 provinces over the coming days including:
Sukhothai, Phitsanulok, Phetchabun, Phichit, Nakhon Sawan and Uthai Thani
Nakhon Ratchasima, Chaiyaphum, Khon Kaen, Maha Sarakham, Kalasin, Roi Et, Yasothon, Sisaket and Ubon Ratchathani
Chai Nat, Lopburi, Saraburi, Suphan Buri, Singburi, Ang Thong, Ayutthaya, and Pathum Thani
People living near the Chao Phraya River in Bangkok, Nonthaburi and Pathum Thani were put on alert from rising water levels between October 7 and 10. The National Water Command Centre (NWCC) expects the water level on the river to rise by 30-40 centimeters.
The NWCC also warned of possible floods from rising water levels in reservoirs which could lead to flash floods and landslides in Phetchaburi, Prachuap Khiri Khan, Chumphon and Ranong.
People living near the Chi River in six northeastern provinces were also put on extra alert from rising water levels between October 4 and 15 including Khon Kaen, Maha Sarakham, Kalasin, Roi Et, Yasothon, and Sisaket.