Som tam nua near siam makes the spiciest larb i've found in bangkok. Their regular spice level will already make most tourists sweat but tourists keep ordering 'pet maak' (very spicy) thinking they can handle it. Watched three different groups send their larb back last week because they couldn't eat it. Kitchen uses bird's eye chilies and doesn't tone anything down - this isn't the adjusted-for-tourists version. Start with 'pet noi' and work your way up on visits. The larb itself is incredible - proper isaan-style with toasted rice powder, mint, and lime