Rice noodles or ramen
If it will be consumed within a day or two, the sauce can be prepared ahead of time. Combine 2 parts soy sauce, 2 parts brown sugar, and 1 part white vinegar. Store in a leak-proof container (I prefer mini-Nalgene bottles).
Boil the noodles according to package directions. If you're using ramen, get rid of the seasoning packet. (Use it later or just ditch it all together. No one really needs that much sodium and MSG in the same sitting.) When the noodles are cooked, drain them, add the sauce, juice from the lime, peanuts, and return to heat until all ingredients are heated thoroughly.
I strongly recommend you add some of the extras to this dish, at least red pepper and garlic to taste. As usually, white sugar or honey can be substituted for brown sugar. A fried egg or two is also a classic pad thai staple. This can be prepared in a separate pan and added at the end. Chicken is also nice. Carrots can be added while cooking or at the end with sprouts to make a great cold garnish.