Athip Jittarerk
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My southern friends have consensus that this eatery is one of the best southern eatery in Bangkok, so if you seek authenticity, this is your choice.
My recommendation is focusing on southern curries and dishes, not seafood, which are fine, but you just don't have to be here for relatively bland seafood comparing to other southern dishes.
Hot, spicy and herbal stir-fry dishes are worth trying. Yellow curry should not be missed. Fish kidney curry (Gaang Tai Pla) here is a must and prepare for extreme taste like no other southern eateries in Bangkok.
Lastly, the battered-fried small shrimps is simply an awesome snack to alleviate the heat from other dishes.