This crumbling shack is living proof that, where authentic Thai food is concerned, ambience is often considered more a liability than an asset. Fittingly, Jay So has no menu as such, but a mortar and pestle and a huge grill are the telltale signs of ballistically spicy sôm đam (green papaya salad), sublime herb-stuffed grilled catfish and other Isan specialities. Look for the white, Pepsi-decorated shack about halfway down Soi Phiphat 2.