Jae Fai is a legendary street restaurant in Bangkok. Though more expensive than typical street food, it's worth every penny.
Jae Fai is still definitely no-frills and only accepts payment in cash. Ms. Fai or Mom, who is ageless, still cooks every dish herself over charcoal burners. The wait can be long so I recommend having our staff order ahead for you to be ready at a certain time. After a walk through the Night Flower Market (15 minutes by boat from The Siam) take a tuk-tuk to Maha Chai Road and Jae Fai. For two people, I suggest ordered this at minimum: Crab Omelet, Drunken Noodles with seafood (Phad-kee-mao Talay), Laad Na with crispy noodles, Beef with Garlic.
My friend and I were fortunate to be guests of Jason at Jae Fai, and it was perhaps the highlight of my trip to Bangkok. The crab omelette is not something I would have ordered on my own, but oh my god was it good! The food was great, and the experience even better. Highly recommend.