At least 244 people have been killed in floods in Thailand since mid-July, the Department of Disaster Prevention and Mitigation said. Another 167 have died in neighboring Cambodia and 15 in Vietnam in what a United Nations agency said was the worst flooding to hit parts of Southeast Asia in 50 years.
"The full extent of damage has yet to occur, in particular the full impact of water flow from the upstream Mekong River," the U.N.'s Office for the Coordination of Humanitarian Affairs said in a statement
In Ayutthaya, about 105 km (65 miles) north of Bangkok, 1,700 prisoners were evacuated from a prison in the old town, clinging to a rope stretched between its gates and a heavy truck as flood water swirled around them.
Somsak Rangsiyopas, deputy director-general of the Correction Department, said water nearly 2 meters (six feet) high had inundated the prison and the area around it.
"We had to the use rope to get people out of the prison due to the strong current," he said, adding that the prisoners were
being transferred to nearby jails.
This week, the 400-year-old Chai Wattanaram temple in Ayutthaya, a World Heritage Site, was flooded.
A big industrial estate in the area with more than 40 factories, many of them Japanese-owned, had to close on Wednesday because of flooding, newspapers reported.
The Center for Economic and Business Forecasting, part of the University of the Thai Chamber of Commerce, said on Thursday it had cut its forecast for gross domestic product (GDP) growth this year to 3.6 percent from 4.4 percent because of the floods.
It estimated the negative impact at between 1.0 and 1.3 percentage points of GDP but said that was offset a little by continued strength in exports, which it now expected to grow 22.6 percent this year rather than 16.1 percent.
Dams are struggling to cope with the flow of water caused by unusually heavy monsoon rain, which normally falls from August to October.
Director general of the Irrigation Department, Chalit Damrongsak, said water would have to be released from the Bhumibol dam in Tak province 420 km (260 miles) northwest of Bangkok, which was 97 percent full, even though that would add to problems further down the Ping river.
That river flows into the Chao Phraya, which flows through Bangkok. The capital has seen only minor flooding and authorities say the inner city should be safe.
Weather forecasters in Vietnam said flooding in the Mekong Delta should peak in the next four days.
At least 15 people, including nine children, have died due to floods since late September in Vietnam's central and southern provinces, state media said.
Dozens of houses had been swept away in the Delta and 27,700 more were under water, state-run news website VnExpress said.
In Cambodia, 167 people have died in floods and more than 160,000 homes were under water, the Cambodian National Disaster Management Committee (CNDMC) said.