Flood victims in Central Thailand continue to come down with disease, according to Public-Health officials. The number of sufferers has topped half a million.

And irrigation officials warn that floods could worsen with the approach of Typhoon Cimarron late next week.

"The typhoon is forming in the Pacific near the Philippines and is expected to hit Vietnam about November 1 before moving over Thailand a few days later," said Royal Irrigation Department director-general Samart Chokanapitak.

The department is keeping a close eye on water levels at dams, he added.

Meteorology Department director Suparerk Tansriratanawong said the magnitude of Typhoon Cimarron could not be determined until Tuesday.

Meanwhile, Ministry of Public Health permanent secretary Dr Prat Boonyawongvirot revealed that more than 574,000 people had been treated for diseases brought on by flooding.

Athlete's foot is the most common affliction, followed by rashes, colds and fever.

"We found 40 per cent of residents in flood-hit areas had athlete's foot," he said.

"What makes me worry is disease will get worse thanks to higher concentrations of pollution in water," he said.

He was concerned about the potential for sickness from leptospirosis and digestive diseases.

The ministry has sent more than 100 mobile medical teams to flood areas.

One way to reduce water contamination is more ablution barges, Prat said. The barges collect and dispose of waste from flood areas before it can pollute waterways. Several have been sent to Ayutthaya and Angthong.

"At least 400 more are urgently needed. Those wanting to make a donation for the barges can contact our flood centre at 082 590 1994 between 8am and 8pm," he said.

The irrigation department is satisfied flooding is easing.

Chao Phaya levels are falling further north, with water volume at Muang district in Nakhon Sawan 3,800 cubic metres a second (cmps) yesterday, down almost 10 per cent from a day earlier.

Levels are also falling in Chai Nat, Ayutthaya and Bangkok. Yesterday, flow rates into Bangkok were 3,373 cmps, 98 cmps down on Friday.

The Royal Navy predicted the river's high-water level at Bangkok would be 2.06 metres above sea level and should occur at 1.49pm.

"However, this won't last for long," Samart said.

Meanwhile, the crew of the Agriculture Ministry relief helicopter that crashed on Friday remained in a coma at a Nakhon Sawan hospital.

His Royal Highness Crown Prince Maha Vajiralongkorn donated money to assist the families of pilot Lt-General Apai Phunuchapai and his mechanic 2nd-Lieutenant Narong Phosawat.