Thailand's government has warned it may not be able to protect the capital, Bangkok as flood waters encroach.
Thai prime minister Yingluck Shinawatra said some sluice gates would be opened to allow a controlled release of water through parts of the city. She has described the situation a "national crisis".
A surge of water caused a 20m (65ft breach in a levy protecting a canal used for tap water that feeds downtown areas in the city of 9.7 million people, Chareon Passara, governor of the Metropolitan Waterworks Authority, told reporters today.
Authorities have since managed to control the overflow, he said.
"We have to drain the water into the sea as much as we can," said Ms Shinawatra . "As there are massive amounts of water, we can't control its direction. We will empty it through our drainage networks at the maximum capacity."
Ms Yingluck had vowed to protect the capital from floods that forced the closure of thousands of factories to the north that supply parts to companies such as Apple Inc. and Toyota Motor Corp. The nation's worst flooding in five decades has killed 320 people and left millions scrambling for dry ground.
Thailand's benchmark SET Index fell three per cent, the most in Asia today and the local currency, the baht weakened one per cent to €0.65.
The government earlier today warned residents living near Prapa canal, which runs from northern Bangkok to an area of the city near Victory Monument along an elevated train line, to be vigilant against floodwaters.
"If we can't pump water out on time, there is a chance Bangkok may be swamped," Pracha Promnog, head of the national flood center, said in a phone interview with Thai television today. Suvarnabhumi Airport, Thailand's main international airport, is operating normally and protected with a 3.5mr barrier to prevent floods. In the worst-case scenario of the facility being flooded, airlines would be asked to relocate operations to the U-Tapao airport in the eastern province of Chonburi.
Rainfall about 25 per cent more than the 30-year average filled upstream dams to their capacity, prompting authorities to release large amounts of water this month down a flood plain the size of Florida.
The waters have affected 14,254 factories and businesses in 20 provinces, leaving 664,567 workers at risk of losing jobs, according to the Labour Ministry.
The floods have swamped industrial estates north of the capital with as much as 3m of water. Japanese carmakers led by Toyota, Honda Motor Co. and Nissan Motor Co. may lose more than €360 million because of the floods, according to Kohei Takahashi, an analyst at JPMorgan Chase and Co in Tokyo.