Thailand's government has ordered a five-day holiday for much of the country so that residents in and near Bangkok can escape what authorities say is an imminent massive flood.

Tens of thousands of people packed roads Wednesday in whatever vehicles they could find. Store shelves were empty with some supermarkets rationing bottled water and other essentials.

Bangkok so far has been spared the flooding that has inundated the city's suburbs and other parts of Thailand.

But Prime Minister Yingluck Shinawatra says the Chao Praya River is on the verge of overflowing its banks, coinciding with an unusually high tide. She says floodwaters in the city could be as deep as 1.5 meters by the end of the week.

The Thai navy has deployed a fleet of ships to the Chao Praya River to use their propellers and try to speed the flow of water through the city's canals and out to sea.

Massive monsoon rains have caused severe flooding across southeast Asia, killing hundreds of people since July.