Nam prik is the oldest and most fundamental category of Thai cooking — pounded relishes and chilli pastes that are the backbone of everyday Thai eating. Each region has its signature version. Served communally with raw and blanched vegetables, fried fish, and rice. Mortar-based, not blended.
Garlic and chillies pounded first into rough paste as flavour base. Shrimp paste or dried shrimp next for umami. Then signature ingredients defining the specific nam prik. Seasoning with fish sauce, lime juice, palm sugar. Texture varies but none are puréed — irregular texture is the point. Nam prik pao (roasted chilli jam) is the exception — cooked into smooth oily paste used as condiment and cooking ingredient.
Nam prik kapi (most fundamental): pound garlic and Thai chillies to paste, add shrimp paste, pound, season with fish sauce, lime juice, touch of sugar. Serve with raw green beans, cucumber, Thai eggplant, blanched morning glory, fried mackerel. That combination is the most Thai meal there is. Nam prik pao keeps weeks in the fridge and makes everything better.
Using a blender. Not roasting chillies before pounding (for charred relishes). Making it too mild — it's eaten in small amounts with lots of rice. Not serving with proper accompaniments. Treating it as a sauce rather than a relish.