Thailand has had its worst floods for half a century after months of unusually heavy rainfall, with 356 people killed since late July and more than 110,000 forced to move to shelters. About 2.5 million people have been affected, with water covering an area the size of Kuwait.
Yingluck urged residents to move possessions at least a metre above the ground. In some parts of the city, water levels have already reached double that height.
On Saturday she said it could be six weeks before the waters subside. The situation is likely to be complicated by high tides due next weekend.