The 577 figure is for a modest stall plate. Sit down in a tourist area restaurant and the plate grows to 350g with a second egg and a heavier pour of oil, and you are at 750 to 800 calories without changing the recipe. The rice noodles alone are about 215 calories per plate, the sauce is another 70, and the cook's ladle of oil is 120 or more depending on how generous they are.
The sauce is the sneaky part. Pad thai sauce is tamarind, fish sauce and a lot of palm sugar, about 15g of sugar per plate. That is why it tastes sweet even when it looks savoury. Squeezing the lime over it does not cancel anything, it just balances the taste. The crushed peanuts on the side are 60 calories per tablespoon, so if you spoon on three, that is a whole extra egg's worth.
Compared with the other stall noodle plates, pad thai sits in the middle. Pad see ew is heavier at 679, rad na is lighter at 397. If you are picking one plate a day from the noodle cart, pad thai at 577 is fine. It only becomes a problem when it is the 40 baht second dinner after a full meal, which is how a lot of people actually eat it.