Floodwaters were also approaching a main road near the city's Mo Chit bus terminal, a major gateway to northern Thailand. But the bus station remained open, traffic police chief Uthaiwan Kaewsa-ard said.
Three months of intense rainfall have fuelled Thailand's worst flooding in half a century, swamping much of the country since July and leaving 506 people dead, according to the government.
Floodwaters have begun receding in some provinces north of Bangkok, but they have built up around the city, which stands in the way of the water's natural flow south toward the Gulf of Thailand.
So far, authorities have ordered evacuations in eight of Bangkok's 50 districts, while seven others are either heavily or partially flooded. Yesterday, floodwaters began lapping at Bangkok's largest outdoor shopping zone, the famed Chatuchak Weekend Market, a major tourist attraction north of the city's central business district.
Water was flowing past the market's eastern side. In the last few days, it has also begun moving southward in adjacent Lad Phrao, a district studded with office towers, condominiums and a popular shopping mall.