Thailand's prime minister said on Tuesday she would miss an Asia-Pacific summit in Hawaii this weekend, postponing her debut on the world stage to deal with the kingdom's worst floods in half a century.

The announcement came as the death toll from the three-month-old disaster climbed to 527 and the floodwaters advanced deeper into the capital.

Prime Minister Yingluck Shinawatra, facing the first crisis of her fledgling leadership, had been planning to brief leaders at the Asia-Pacific Economic Forum (APEC) about the crisis and boost investor confidence in the country.

But with the mass of water now threatening the heart of Bangkok, a city of 12 million people, Yingluck said she would send Deputy Prime Minister Kittirat Na-Ranong, who is also the commerce minister, on her behalf.

"I think that at this time all Thai people must help" in the flood crisis, she told reporters about her decision.

Yingluck said she would discuss with her cabinet whether to attend a gathering of Southeast Asian leaders in Bali next week.

The November 12-13 APEC meeting would have been the first international summit for Yingluck, a political novice and sister of fugitive former premier Thaksin Shinawatra who only came to power three months ago.

APEC is a 21-member Asia-Pacific bloc that encompasses more than half of the world economy and includes the United States, China, Japan and Australia.

Yingluck's administration has faced criticism over its handling of the flood crisis, and heading to Honolulu in the midst of the disaster would have provided easy ammunition for her political opponents.

The Thai floods, triggered by months of unusually heavy rains, have damaged the homes and livelihoods of millions around the country.

The waters also forced the closure of thousands of factories -- interrupting global supply chains, putting more than half a million people temporarily out of work and costing the economy billions of dollars.