Cellophane noodles (aka rice vermicelli)
Chilli, red or green but preferably bird's eye
The correct noodles are necessary. They may be hard to find if you don't know what you are looking for; there are many types called rice vermicelli but these are very very thin, in a bundle, and almost translucent.
Combine equal amounts of vinegar and fish sauce and add sugar. You may have to taste this; it should be balanced between the three. This can be made ahead.
Heat 1-2" of oil until *very* hot. Test if it's hot enough by sacrificing a noodle end; if it lies there comfortably, it's too cold. If it puffs up spectacularly all going fizz, that's ready and you can repeat the process with all your noodles. (Wet them a bit first and they'll stay crispy for longer.)
Once that's done, most of your oil should be used up, so you can cook the egg in the same pan. Stir it around like you would for egg fried rice, adding the fish sauce mixture.
Add the prawns and the chopped veg. type ingredients, stir all up together, and you're done.