Central Thai and Isaan primarily — South uses lime more frequently; tamarind trees are planted outside most Thai homes throughout the country
Tamarind (Tamarindus indica) provides the primary souring agent in Thai cooking — fruity, deep acid that is distinctly different from lime's sharpness or vinegar's one-dimensionality. In Thai kitchens, tamarind is used in three forms: fresh pods (ripe, sweet, often eaten as a snack), compressed block tamarind (makham piak, dried pulp with seeds and fibre, reconstituted in warm water), and ready-made concentrate. The block form is the professional standard — you tear off a golf-ball amount, soak in warm water for 5 minutes, then squeeze and press through fingers to extract the thick paste, discarding seeds and fibre. Concentration of the resulting liquid is the critical variable in most dishes.
Tamarind's deep fruity acid interacts differently with fish sauce than lime does — it softens the brininess while adding complexity, which is why pad thai tastes warm and rounded rather than sharp.
{"Block tamarind to warm water at approximately 1:3 ratio; soak 5 minutes then press through fingers","Always strain through fingers or a sieve — seeds and fibre in the dish is a service failure","Reduce the strained liquid in the wok for pad thai and pad see ew to concentrate sweetness","Ripe (sweet) tamarind and sour (unripe) tamarind are different ingredients with different applications","Tamarind concentrate in jars is acceptable for speed but often too dense — dilute by half before using"}
For the most deeply flavoured tamarind water, use hot (not boiling) water and let it soak while you prepare other ingredients. The depth of colour should be that of very dark tea — thin, pale tamarind water adds liquid but not much flavour. Good block tamarind should smell fruity and sour, not musty.
{"Using lime juice as a direct substitute — lime is sharp and bright, tamarind is deep and fruity","Adding unworked block tamarind directly — it will not dissolve evenly and seeds create choking hazard","Under-soaking block tamarind and getting under-extracted thin liquid","Using tamarind concentrate at full strength for salad dressings — it overpowers all other flavours"}