BANGKOK - Floodwaters that have devastated Thailand's industry and agriculture seeped into outer Bangkok on Friday as the crowded capital's residents braced for the impact, uncertain if they will soon be hopping over puddles or fording waist-high streams just outside their windows.

Thailand's prime minister urged residents of the city of 9 million people to get ready to move their belongings to higher ground. Key gates on flood-control canals in the capital have been opened in a risky move to drain the high waters into the sea, but it's not known how much will overflow onto streets.

An Associated Press team saw water entering homes and rising to knee level Friday in a northern district along the capital's main Prapa canal. Damage so far was minor and not affecting Bangkok's main business district.

Prime Minister Yingluck Shinawatra said the Prapa canal was a big concern and urged people "not to panic."

Newly released data showed the devastation the flooding has caused in both agriculture and industry.

The U.N.'s Food and Agriculture Organization said flooded areas of the country cover 12.5 per cent of the total land under cropping.

"Although no precise crop damage estimates are yet available, the main rice season at the critical growth stage is likely to be affected the most," said an FAO statement.

Thailand is a major agricultural exporter and has been the world's top rice exporter for decades. The FAO said it expected its estimate to rise as dams allow run-off of water.

Thailand's Labor Ministry said the flooding has affected 14,818 workplaces and 678,227 workers. The total includes the damage from five major industrial estates north of Bangkok forced to shut operations in the past few weeks after being inundated. Among those affected are Japanese carmakers Toyota and Honda, forced to suspend major assembly operations, and a slew of automotive parts makers.

The electronics industry has also suffered, with the best known victim being U.S. hard drive maker Western Digital, which has two major production facilities in the flooded zone.

Economic analysts say the floods, the worst in half a century, have cut Thailand's 2011 GDP projections by as much as 2 percentage points. The latest damage estimate of $6 billion could double if floods swamp Bangkok.

The government said at least 342 people have died in the floods since July. Some towns were submerged under water more than six feet high (two meters high), and the uncertainty in the capital may persist for up to three weeks.

Many fear the worst is yet to come, as the massive volume of water flowing from north and central Thailand pushes into Bangkok and its network of canals.

Bangkok Gov. Sukhumbhand Paribatra said managing the Prapa canal was a "top priority" but vast pools of runoff draining through it from the north are expected to intensify. An immense network of sandbagged barriers could deteriorate under pressure from the water.

Yingluck also invoked her powers under a disaster law that give her overriding authority over all other official bodies, including local governments, to fight the crisis. It should allow better co-ordination with the municipal authorities in Bangkok and helps project Yingluck as a take-charge leader, after weeks of seeming indecision and confusion.