The country is also bracing for more high tides in the coming week, according to Thailand's Flood Relief Operations Command. High tides cause rivers to back up, subsequently raising water levels.

Thai Prime Minister Yingluck Shinawatra said authorities are trying to drain water into the sea as quickly as possible, but the disaster has proved arduous.

"I would like to apologize to the public because it has been difficult to make advanced notice about the floods," she said, according to the Thai News Agency. "There are many factors beyond our expectation. Informing too early could cause panic and mistakes could happen easily, but people should be alert and closely follow up the situation."

The government has set up more than 1,700 shelters nationwide, and more than 113,000 people have taken refuge inside.

It had hoped that strengthening flood barriers and widening canals would keep populated areas safe.

But now it is trying a different technique: opening floodgates to relieve pressure on dams and levees and send the water toward the sea.

The decision to divert water through canals in Bangkok means parts of the city, and its surrounding suburbs such as Rangsit, are flooded.

The flooding, which follows months of monsoon rains, has already killed 356 people, with nearly 9 million others affected, authorities said.

Overall damage from the floods could top US$2 billion, with the worst yet to come as the waters destroy shops and paralyze factories nationwide, the Thai Finance Ministry said.