More housing and industrial areas on the outskirts of Bangkok are now being flooded as barriers give way to water flowing into the city from northern Thailand.
The ABC reports there are growing fears that sand barriers protecting the north-east of the capital will fail.
Monsoon floods have killed at least 315 people since July and damaged large areas of farmland.
Army trucks evacuated the Navanakorn estate, on the city's northern fringe, on Tuesday after a flood protection barrier failed.
The industrial estate, where 200,000 people work in factories and live in apartments, had been dry and declared safe by the government on Monday.
The ABC reports the water is gradually creeping closer to the main part of Bangkok.
Currently about a third of Thailand's provinces are affected by the floods.
But most of Thailand main tourist attractions - including the southern islands of Samui, Phi Phi and Phuket - have been unaffected and Bangkok's main airport, Suvarnabhumi, is operating as usual.