UPDATE 1-Western Bangkok warned floods may last until new year
* PM says Thailand will recover soon
* Parts of Bangkok western districts could take longer to drain
* Clinton pledges long-term U.S. support for Thailand, offers $10 mln aid
* Floodwaters in most estates recede; businesses return
* Death toll rises to 564 since July
By Ploy Ten Kate and Paul Eckert
BANGKOK, Nov 16 (Reuters) - Floodwater in parts of Thailand's capital, Bangkok, is receding after weeks of inundation but Prime Minister Yingluck Shinawatra and water experts said residents in some western districts could still be suffering into next year.
However, Yingluck reassured investors at a news conference with United Nations Secretary-General Ban Ki-moon on Wednesday that Thailand would get back on track quickly and had a long-term strategy for redesigning its water management system.
"We'll recover soon," Yingluck said, adding that restoring some infrastructure could be completed within 45-90 days.
She said eastern Bangkok, where two industrial estates are still surrounded by water, should be flood-free by the end of the year but draining water from western districts was harder.
Thailand's worst flooding in at least five decades has claimed 564 lives since July, with water flowing slowly down from the north, inundating agricultural and industrial areas in the centre before swamping parts of Bangkok from late October.
U.S. Secretary of State Hillary Clinton, also on a visit to Thailand, offered $10 million in aid, in addition to $1.1 million already offered, for humanitarian assistance, equipment and training in emergency response and disaster prevention.
"While we are focused now on the immediate needs of the Thai people, we will also be here for the long run," Clinton told a news conference.
She said Washington would "support Thailand's economic recovery as a trade, investment and development partner".
U.S. officials would work with Thai military and civilian organisations to get the city's swamped Don Muang airport up and running to facilitate relief missions, Clinton added.
Bangkok's main Suvarnabhumi airport, which is protected by a dike about 3.5 metres (11.5 feet) high in the east of Bangkok, is operating as normal.
Anond Snidvongs, executive director of the government's Geo-Informatics and Space Technology Development Agency, said residents living in certain low-lying areas in the west would have to live with water for a while longer.
"In the western area, the capacity of the drainage system was limited from the start," Anond told Reuters, adding there were also fewer canals than in the east.
"What we're trying to do is add more water pumps and control the opening and closing of sluice gates in line with the high and the low river tides, as much as possible," added Anond, who is acting as an adviser to the government.
He said some districts in western Bangkok could still escape flooding completely, and it should take only two or three weeks for main roads to dry out.
Floodwater has reached part of the low-lying Rama II Road, a main highway through the west of Bangkok to the rubber-growing south of Thailand, which has not been affected by the floods.
GETTING BACK TO NORMAL
Most of Bangkok's central business district remains dry.
In the north of the capital, the old Don Muang airport, used mainly for internal flights, is still closed but areas to its south are starting to dry out.
An army of street cleaners was at work on the main Pahonyothin Road, disposing of trash and dead plants and removing thick layers of dirt left behind by the water.
Streets in office areas that had been deserted only a few days ago were getting back to normal, with outdoor eating areas and market stalls up and running again. Most of the cars that had been parked for weeks on elevated roads had gone.
Top Thai retailer Central Pattana Pcl said it would reopen Ladphrao mall, one of its biggest, on Nov. 18. Its flood-hit Pinklao mall reopened on Nov. 13.
Evacuation orders had been issued in a third of Bangkok's districts, mostly in the north of the densely populated city of 12 million people.
Yingluck, whose government only came to power in August, said last week about 120 billion baht ($3.9 billion) had been set aside for the immediate flood recovery effort, a figure that rises to 130 billion baht when local government funds are added.
In the east of Bangkok, floodwater continued to surround two industrial estates but defences were holding up and some plants, including that of Honda Motor Co, were back at work.
Isuzu Motors Ltd said it planned to restart its Thai plant, halted by a shortage of parts due to the flooding, on Nov. 21 rather than Nov. 18.