Many people in Bangkok had breathed a sigh of relief earlier after barriers protecting the capital from the country's worst flooding in decades held firm.
Officials in charge of fighting the flood had suggested that Bangkok would be spared thanks to the city's complex system of flood walls, canals, dikes and underground tunnels that help divert vast pools of runoff south into the Gulf of Thailand.
Relentless monsoon rains that began in late July have affected two-thirds of the country. The nationwide death toll is 307.
Authorities ordered a new evacuation Monday in an industrial park north of Bangkok as the disaster's economic impact worsened.
At least four other major industrial parks were flooded, leaving nearly 100,000 workers without jobs and disrupting the automotive and electronic industries.
The Associated Press contributed to this report.