Deputy Prime Minister Plodprasop Suraswadi said on Wednesday that water running off from high areas in Aranyaprathet and Muang districts of Sa Kaeo was flowing towards Kabin Buri and expected to hit the town area by Friday.
Some areas could expect water up to two metres deep, he said on an FM97.0 news programme.
The government on Tuesday announced it expected Kabin Buri to be dry within a week -- provided there was no new rainfall in the district, but the water is coming in from outside the district.
Mr Plodprasop unveiled the new assessment on Wednesday, admitting the plight of people in the flooded districts would get worse, not better.
Mr Plodprasop warned the deluge would likely flow into Si Maha Phot and Pachantakham districts two days after it inundates Kabin Buri and slowly flows out of the town.
"The water will take roughly about two days to reach Si Maha Phot and Pachantakham from Kabin Buri," he said.
Muang district of Prachin Buri will face an additional inundation afterwards, followed by Ban Sang district before the water finally flows in to the Bang Pakong River and flood districts in neighbouring Chachoengsao and then on to the Gulf of Thailand, he said
Ban Sang district in Prachin Buri and neighbouring Nakhon Nayok and Chachoengsao could also be hard hit as they absorb water flowing in from all three provinces, he added.
Twenty-seven provinces in the country are flooded with 36 people confirmed to have lost their lives as a result, according to the Disaster Prevention and Mitigation Department statement on Tuesday.
In Khon Kaen, water has flowed from Chaiyaphum to six districts at an average height of around 60cm and it was likely that the flood would spread.
At least 7,000 rai of agricultural land has been affected by the flood so far, provincial governor Somsak Suwansucharit said.
He said the flood from the Chi River will arrive in Khon Kaen province this weekend and it is expected to linger for about a month.
Economic areas in Muang district were also at risk of flash flooding as Ubonrat Dam was discharging about 40 million cubic metres of water a day. The dam currently holds 1.83 billion cubic metres of water, or about 75% of its capacity.
Meanwhile, floodwaters were threatening Rojana Industrial Park in Uthai district in the central province of Ayutthaya.
About 100,000 rai of rice fields close to the industrial park had been flooded after two weeks of continual heavy rain, Pheu Thai MP for Ayutthaya Witthaya Buranasiri said.
The large amount of rainwater had nowhere to go because canals in the area were lower than the Chao Phraya River.
Authorities were preparing to install a number of large pumps to drain water into the Chao Phraya, Mr Witthaya said, adding that the Rojana industrial facility and a nearby community would not be affected.
In Pathum Thani, three districts -- Muang, Sam Kok and Lam Luk Ka -- were flooded, causing problems for 4,569 families.
In Nakhon Ratchasima, the water level at Lam Prapleng reservoir still exceeded its capacity, so about nine million cubic metres will be discharged per day into natural canals, resulting in the floods in seven tambon of Pak Thong Chai district or about 3,500 rai of farm land.
Mongkol Pakdinok, 59, a farmer in tambon Suk Kasem, said he planted a rice crop on his 10 rai of land adjacent to a canal about three months ago, but the plants, which were near harvesting, had now been under water for two days. In another couple of days, the rice woud begin to die.
Another 800 rai of rice planted in this area was also reported to be under water.