Tom Saap — Isaan Spicy Pork Bone Soup / ต้มแซ่บ

Isaan — considered the national soup of northeastern Thai cooking; available at every Isaan restaurant; the pla raa component is the definitive Isaan marker

Tom saap is Isaan's spicy, sour pork rib soup — related to Central Thai tom yum in its hot-sour profile but heavier, more rustic, and with pla raa as a seasoning element rather than standard fish sauce. Pork ribs (or a mix of ribs, knuckle, and offal) are simmered in water with lemongrass, galangal, kaffir lime leaves, and bird's eye chillies, then seasoned with pla raa (fermented freshwater fish), lime juice, and dried chilli powder. The 'saap' (delicious) in the name reflects its place in Isaan cuisine — it is considered the Isaan comfort soup, eaten at communal meals, with sticky rice. The pork should be tender off the bone; the broth should be sour-hot-savoury.

Tom saap's combination of pork collagen richness, aggressive sourness, and the specific fermented note of pla raa creates a broth that is simultaneously challenging and deeply satisfying — the Isaan equivalent of a great French pot-au-feu in terms of its position in the regional food culture.