When I was in Bangkok, if I came across a restaurant NOT serving this dish I would be amazed! It's served everywhere and is incredibly popular (and delicious).
I found the best experience would pretty consistently be from street stalls and night markets rather than restaurants. The Sukhumvit Soi (38) night market has heaps of stalls offering it. Get the sky train to Thonglor station and it’s just a short walk to the wonderful land of mango sticky rice!
Kate almost 7 years ago