* Receding waters in northe reduce flood risks in Bangkok
* High tides still pose risk to some areas
* Floods to push up global prices of rice, computer hard drives
* At least 377 killed since July; 2.2 million affected
By Jason Szep and Apornrath Phoonphongphiphat
BANGKOK, Oct 29 Receding floodwaters north of Bangkok have reduced the threat to the Thai capital, the prime minister said on Saturday, but a rise in coastal high tides in the Gulf of Thailand will still test the city's flood defences.
"If things go on like this, we expect floodwater in Bangkok to recede within the first week of November," Prime Minister Yingluck Shinawatra said on national television.
Bangkok's main waterway, the Chao Phraya River, has swollen close to its brink during unusually high tides, causing some flooding in nearby areas. Buildings across Bangkok have been sand-bagged for protection. Many residents have fled the city or stocked up on water, food, life jackets and even boats.
Thailand's worst floods in half a century have killed 377 people since July, wiped out a quarter of the main rice crop in the world's biggest exporter, forced up global prices of computer hard drives and caused delays in global auto production after destroying industrial estates.
Prices of eggs in Bangkok have quadrupled as jittery residents stockpiled staples. Commerce Minister Kittiratt Na-Ranonga assured flood victims they would have enough bottled drinking water, dairy products, pork and chicken.
Cash was also in heavy demand. The Bank of Thailand has repeated that there is enough money circulating to meet demand for three months following a crush of withdrawals. Nearly 400 bank branches have closed across the country due to the floods.
The floods have submerged 4 million acres (1.6 million hectares) of land, an area roughly the size of Kuwait or Swaziland, turning entire cities into urban reservoirs.
Yingluck said the ebbing of floodwaters in northern provinces, thanks to the draining of water into the Gulf of Thailand through canals and pumps, had reduced the risk of large volumes of run-off water bearing down on Bangkok. The city sits only two metres (6 1/2 ft) above sea level.
"In this critical situation, there is some good news for us. Our water-management plan went smoothly during previous days," Yingluck said.
The Chao Phraya is expected to rise to as much as 2.6 metres (8.5 ft) above sea level on Saturday during high tides, the government said this week when it declared a five-day holiday from Thursday to allow people to leave.
Many foreign governments have warned their citizens against non-essential travel to the city of 12 million people, one of Asia's largest. City hotels have emptied and gone quiet. Many locals have headed for the seaside town of Hua Hin and the eastern resort city of Pattaya, where hotel rooms are scarce.
Bangkok's governor late on Friday ordered the evacuation of a fourth district, Thawi Whatthana, in western Bangkok. Evacuations have now taken place in four of Bangkok's 50 districts -- Don Muang, Bang Phlat, Sai Mai and Thawi Whatthana -- all of which have suffered floods in recent days.
FLOOD WARNING IN WESTERN BANGKOK
Local authorities expect Thonburi, on the west bank of the Chao Phraya, to be inundated within three days and Yingluck said levels should remain high for days due to a lack of canals. Seventeen roads across Bangkok already have been closed.
Japanese engineers have been flown in to advise on how to protect Bangkok's main international airport, Suvarnabhumi, and the city subway system. Authorities have built a 23.5 km (15 mile) dike around the airport and have reassured travellers it would be safe.
Roads around the Grand Palace, a top tourist attraction, were briefly flooded on Friday along with some streets in densely populated Chinatown during high tide.
Bangkok, which accounts for 41 percent of Thailand's $319 billion economy, has been at risk from run-off water from the north coinciding with the high tide on the Chao Phraya, already at a record high level.
The economic toll continued to mount in Thailand, the second-largest exporter of computer hard drives and Southeast Asia's biggest auto production hub. Global prices for hard drives, for instance, are rising due to a flood-related shortage of major component used in personal computers.
Drive manufacturers have raised prices by 20 to 40 percent and in turn raised prices by a similar amount after water poured into factories this month, said Chuck Kostalnick, Senior Vice President of international electronics distributor Avnet Inc.
"The word we're getting is that prices are going to continue to go up," he told Reuters. "This isn't going to be a one-time event."