The five-day holiday will run from Thursday through to Monday in Bangkok and in 20 provinces affected by the flooding.

Bangkok's Governor Sukhumbhand Paribatra issued an evacuation alert for residents of Don Muang, Bang Phlad and Thawi Wattana districts in the north of the capital.

Bangkok's bus and train stations and many roads are jammed by thousands of people attempting to flee.

People in several northern districts - some of which are now 90 percent submerged by rising waters - have been told they should evacuate immediately.

More than 360 people have died in Thailand's worst flooding in decades.

The crisis is an early test for Prime Minister Yingluck Shinawatra, who took office in August and has previously been criticised for failing to take the flood threat seriously enough.