Five things you should know about Sukhothai noodles:
1. A bowl of noodles is deemed “Sukhothai” when it has pork slices and shredded green beans as a garnish alongside or instead of the usual bean sprouts.
2. The proper flavorings of a bowl of Sukhothai noodles are reminiscent of a plate of pad thai.
3. While Sukhothai noodles can involve any type of noodle, the best (in this person’s opinion) are the angel hair (sen mee) or thin noodles (sen lek), which absorb more of the seasoning while retaining some al dente crunch.
4. It’s hard to stop at just one bowl. Just try it. I dare you.
5. My favorite bowl of Sukhothai noodles can be found at Somsong Pochana (Soi Wat Sangwech, 02-282-0972), which also serves rice with different types of curry (khao gaeng), a good way to while away the time as you await your noodles, and kanom jeen saonang, a type of fermented rice noodle topped with an old-fashioned (and seriously sweet) pineapple-and-coconut-milk sauce.
Courtesy of Winner Dachaiphan and pbinbkk
Bangkok Glutton 
Ahhh I’m so grateful to find information about what distinguishes Sukhothai noodles from, say, tom yum noodles. I’ve had variations of both that have tasted similar, and even my cookbooks in Thai have offered no real explanation. There also seems to be a tendency to use palm sugar instead of white sugar from what I have read/have tried.
Yes, that region is famous for its palm sugar