The Second Hand Book Restaurant, Phang Nga Road
(What's it really called?)
A big plate full for only 45 Baht!
You might not notice the shop but it is right next door to the Bangkok Bank in Phang Nga Road, and if you're a noodle fan then why not order both.
Sorry about the dismal photo but I only get a day off when it rains!
You will also find them among the many food stalls at some of the local fairs and festivals. Just look for their sign.