I've dabbled in a little Thai cooking, and cooked everything too long until a friend of mine explained everything in a way that made clear and perfect sense.
Southeast Asia is a hot place. I was sweating on New Year's Eve, and I grew in in Atlanta without AC. Lot of heat, lot of people, not much wood/fuel. They don't, as many European cuisines do, keep a stew/soup opt bubbling on the stove for hours on end.
There might be hours of prep time, but the cooking is fast, hot, done and out. Like stir-fry.