The Chao Phraya River snakes its way through Bangkok before emptying into the delta at the Gulf of Thailand. High tides at the weekend mean that river levels will rise and, as has been predicted for the past several weeks, the capital's flood-protection system will be put to a critical test.
In the "worst-case scenario" if the levees fail along the Chao Phraya, most of Bangkok will be submerged in water 50 centimetres to two metres deep. There have already been more than 360 casualties from this season's floods, young people and the infirm are being evacuated to the south, and the economic costs, now tallied at $3 billion (Dh11 billion), continue to rise.
There is also the psychological toll as Thais - and sympathetic observers around the world - watch as one of Asia's major capitals comes under such a serious threat. Already blame has been apportioned between the newly elected government and Bangkok's governor, and there are real lessons on land development and flood control for the future.
For the next few weeks, whether or not the levees hold, the capital and the provinces that are flooded will struggle to limit the damage. And the Thai people, as they have done before, will make the best of a bad situation with admirable equanimity.