Stage one of the three-stage emergency plan was declared Wednesday night at Bang Chan Industrial Estate in northern Klong Samwa district of the capital city after water in nearby canal went a meter high above normal levels.
The second stage will be announced if the water raises 1.3 meter above normal, when factories will be told to prepare for evacuation. If the water level goes 1.4 meter high, factories will be warned to evacuate.
The main road at Bang Chan Industrial Estate was under 20-30 cm water high on Wednesday afternoon. Some 8,000 two-tonne "big bag" barriers were placed along the road.
Until now 20 companies have temporarily halted operations for fear of losses due to flood damage.
Bang Chan is home to 93 companies with a total investment of 19.8 billion baht (642.65 million U.S. dollars) and 13,800 workers.
The industrial park has tried to fight against floods at any cost, installing 29 pumps to drain 500,000 cubic metres of water per day.
So far, there have been seven industrial estates in central Ayutthaya and Pathum Thani provinces which were submerged by the most severe inundation in over half a century.
The initial cost of damage was estimated at 16 billion U.S. dollars and the global supply chains for electronic appliances and auto parts disrupted.