Isaan — pla raa som tam is the authentic Isaan preparation; the fish sauce version was developed for Central Thai and tourist palates
Som tam pla raa is the Isaan version of green papaya salad — made with fermented freshwater fish (pla raa) as the seasoning agent instead of or in addition to fish sauce. The pla raa transforms the dressing into something deeper, funkier, and more complex than the coastal-Thai fish sauce version. The fermented fish is used either as raw chunks stirred in at the end (for the traditional version with maximum funk) or as a cooked liquid (the fish is simmered with a little water, strained, and the liquid used). This is the version eaten with sticky rice in Isaan, and is an acquired but deeply regional taste. It is the standard version at most Isaan restaurants — the fish sauce version (som tam Thai) is considered the Central Thai adaptation.
Pla raa som tam has an intensity of flavour that the fish sauce version cannot match — the depth of fermentation adds a fifth-dimension complexity that converts the salad from a bright, fresh composition to something ancient and insistent.
{"Pla raa (not fish sauce) is the seasoning — do not substitute or you make a different dish","The mortar technique is identical to som tam Thai — same dtam motion, same sequence","Pla raa added toward the end of the mortar work — it is salty and the seasoning must be tasted and adjusted","Traditional version includes the whole fermented fish pieces — the texture is part of the dish","Do not omit the palm sugar — it balances the intensity of the pla raa's fermentation"}
Cooked pla raa liquid (simmered and strained) is the compromise for diners nervous about the full-fermented experience — it captures the depth without the intense fishy chunks. Start all new cooks on the cooked version before introducing the raw fermented fish pieces.
{"Substituting fish sauce and expecting the same result — pla raa has a fermented complexity that fish sauce cannot replicate","Over-using pla raa — it is extremely salty; start conservatively and taste","Treating pla raa som tam as identical to fish sauce som tam — the flavour profile is fundamentally different","Not adjusting lime and palm sugar to balance the fermented saltiness"}