The death toll from floods in Thailand has reached 342 and floodwaters are reaching outer Bangkok.

Prime Minister Yingluck Shinawatra urged residents in the Thai capital Friday to move their belongings to higher ground, but she asked them not to panic.

Water rose to knee-level in some places after flooding over canals in Bangkok's northern Lak-Si district, about 16 kilometers from the city center.

Many Bangkok residents are rushing to stock up on food and drinking water, while those in the flooded north have already fled their homes.

The prime minister also invoked the natural disaster law that gives her authority to implement a nationwide disaster relief plan and punish the officials who fail to follow instructions.

The worst flood in 50 years has already hurt Thailand's industry and agriculture in one third of the country.

Heavy rains since July have inundated large parts of Southeast Asia, forcing millions from their homes. Another 336 people have died in Cambodia, Laos and Vietnam. Thousands of people in southeast Asia have been displaced.

On Thursday, the Thai government ordered the opening of Bangkok's floodgates to drain water through the canals to the sea, and relieve pressure on dikes that had kept water out of the city for about a week.