Great lunch after visiting temples, also convenient if you are staying at Khao San Road (I don't recommend you do). There are two stalls next to each other, I originally came here due to the recommendation from @migrationology but honestly, I think I picked the wrong stall.
Nevertheless this was absolutely great and I think the quality of both stalls is about the same.
I ordered clams with chili paste, Tom Yum kung and crabmeat stir fried with curry powder and Chinese celery.
This place is named after Tom Yum, so of course, it was fantastic. The broth was intense with aromatics, sour, salty with just a hint of sweetness, and the spice level was just right. The balance in flavour was about as perfect as it can be. The shrimps were peeled in a way that let the head juices get out, which made the soup extra creamy.
Clams with chili paste (prik pao) is one of my favourite dishes and this version was just right. Sweet, umami-rich, lots of thai basil and garlic and with a decent kick. Just thinking about it now makes me salivate.
The crab was decent, but I prefer a different version of this dish, in which an egg is added to a creamier curry, making a sort of crazy rich scrambled egg.