With knee-deep floodwaters enveloping Bangkok, high tides from the sea are pushing the Chao Phraya River's level in the central city to as high as 2.6 metres above mean sea level, above a 2.5-metre concrete floodwall, the chief of the Thail Navy's Hydrographic Department said Wednesday.

In a TV interview, Vice Admiral Niruth Hongprasert said it was not easy to predict the level of the Chao Phraya more than two to three days ahead, as there are so many unpredictable variables, especially the mass of floodwater flowing from the north.

Submerged Don Muang Airport Closed Down

Early Wednesday, the country's domestic airport, Don Muang, was flooded and closed down.

As of press time, the international airport, Suvarnabhumi, was functioning normally, although authorities could not say for how long can they hold it dry.

Prime Minister Yingluck Shinawatra has issued a warning to residents to brace for as high as 5 feet (1.5 meters) of water if flood walls break down.

Shinawatra has declared a five-day public holiday beginning Tuesday in affected areas, including Bangkok. Schools at all levels in the capital were suspended by the Education Ministry until Nov. 7.