Bangkok has been declared a disaster-affected zone after torrential rain led to widespread flooding, as Thailand's weather agency forecasts thunderstorms.
Major roads were flooded and cars submerged, with people forced to wade through waist-high water, after nearly 300mm of rain fell in only 48 hours.
Bangkok Governor Chadchart Sittipunt said the crisis "poses a risk to people's lives" and could damage public and private property. The situation was most severe near canals, he added.
The Thai military said it would set up shelters and field kitchens to aid disaster relief efforts, while the Bangkok Metropolitan Administration has designated schools as temporary accommodation and asked residents to avoid unnecessary travel.
Supermarkets were crowded with people stocking up on supplies.
"I'm worried too, because I haven't stocked up on food beforehand, and I've never faced this kind of situation alone before, since my parents aren't with me," said teenage Bangkok resident Sansuk Laowatcharakul.
The government on Saturday issued an emergency advisory for people living near canals to move personal items to higher ground. "I wasn't aware enough to consider relocating" before the warning was issued, said Bangkok resident Suppakarn Julavijitphong.
The city's main airport was operating normally, although the tourism authority advised travellers to allow an extra two to three hours to pass through the hub.
Thailand experienced its worst floods in decades in November when at least 145 people died and thousands of homes were damaged in the country's southern provinces.
