How do I make Pad See Ew with Fresh Rice Noodles
I live in Thailand so I feel I'm qualified to answer this question.

The key sauce for pad see ew (ผัดซีอิ๊ว) is figured out from the dish's name. See ew (ซีอิ๊ว) is a Thai soy sauce that is either dark or light and sweet or salty (yes, four versions in total). The dish also contains fish sauce.

In my opinion, pad see ew tastes best using the dark sweet sauce, which has a deep molasses flavour.

Use only sauce made in Thailand and there are no substitutions. Look for this on the label: ซีอิ๊วดำหวาน (dark sweet) or ซีอิ๊วดำ (dark not sweet). Since you probably can't read Thai I suggest you play a spot-the-difference game.

My personal favourite is this sauce but it's hard to get outside Thailand.

If you do substitute using normal soy sauce you pretty much end up with pad khii mao (ผัดขี้เมา).