When it rains in Thailand, it pours.
I do not know of anywhere else where the city streets can fill up with rain as fast as in Bangkok, Pattaya, Phuket and other locations.
Be advised to get a good weather app on your phone and follow the weather.
You could be going out thinking it is just another rain shower and end up stranded in 2 to 3 feet deep water.
Better to be safe than sorry.
Even if you see Thai drivers in this deep water, DO NOT do it!
It is not safe and the road under the water could wash away.