Thailand is just plain hot, hot, hot.
When the temps start spiking above 36+c, it is very uncomfortable to be outside.
Anywhere!
With all the concrete, cities like Bangkok feel even hotter.
However, even at the beach it is to hot to sit out in the sun.
The water is not cold enough to cool you down either.
When you have an agenda full of activities planned, be advised due to the high heat and humidity it will get very uncomfortable where ever you happened to be going.
So humid, your shirt/top will be soaked with sweat in the first 5 minutes.
Traveling around all hot and sweaty is very annoying and uncomfortable.
Unfortunately the only way to be comfortable is to stay in the air conditioning, like at the malls.