Thai food in Thailand is nowhere near as spicy as "Thai Spicy" or even "Hot" Thai food in the states, in my experience. Some places I went it approaches or slightly exceeds "Hot", but on the whole I think the spiciness of Thai food is way overblown.
In my experience the spiciness levels are 1, 2, and 3 meaning 1 - 3 dried or fresh birdseye (or similar) red chilis. It's pretty standardized and 3 is a hot but still pleasant level of spiciness. Thai people aren't competing to see who can light their asshole on fire, they just want good food.