Bangkok Governor Pol General Aswin Kwanmuang on Thursday ordered officials to closely monitor the situation.

Five hundred families living along the Chao Phraya River were advised to brace for flooding during that period and move their belongings to safety beforehand as a precaution.

Aswin cited a report from the Royal Irrigation Department that the river was currently flowing through the Chao Phraya Dam at 1,498 cubic metres per second.

The water level there was said to be more than 16 metres above mean sea level.

As long as there is no further significant rainfall in Nakhon Sawan, Khamphaeng Phetch, Phichit and Uthai Thani, the water level and flow at the dam would remain controllable, Aswin said.

However, seasonal high tide from September 4-8 would raise the Chao Phraya River level in Ang Thong, Ayutthaya and Pathum Thani by as much as 15cm.

Combined with the runoff from the North, Aswin warned, Bangkok riverside residents not protected by the Chao Phraya, Khlong Bangkok Noi or Khlong Mahasawat flood barriers needed to brace for inundation.

That applies to 496 households in 10 districts – Bang Sue, Dusit, Phra Nakhon, Samphanthawong, Bang Kho Laem, Yannawa, Bangkok Noi, Khlong Toei, Khlong San and Rat Burana.

All could be affected and precautionary measures should be taken, Aswin said.

The city has placed 100,000 sandbags near gaps in the flood barriers and another 100,000 sandbags are ready if needed, he said.