And the Organisation for Economic Cooperation and Development has classified the Thai capital among the 10 cities in the world facing the biggest potential impact from coastal flooding by 2070.
For now, Bangkok is relying on a complex system of dykes, canals, locks and pumping stations to keep the rising waters at bay.
The flood protection efforts, however, failed to prevent an onslaught of run-off water from the north from swamping at least one-fifth of the capital.
The murky floodwaters, triggered by three months of heavy monsoon rains, are edging in on Bangkok's glitzy downtown area, threatening luxury hotels, office buildings and shopping malls. Rapid urbanization is one reason why the inundations are affecting the sprawling city so badly, according to experts.
As the area that needs flood protection gets larger and more built-up, the water "has fewer places to go", said Francois Molle, a water management expert at France's Institut de Recherche pour le Developpement.
Molle said that in the long term, Bangkok would eventually be under water. "The only question is when."