The main ingredients in traditional Thai peanut sauce are roasted peanuts, coconut milk, palm sugar, tamarind and red chili peppers. Various herbs and spices play an important role in adding depth of flavor to the sauce.
A comprehensive recipe for Thai peanut sauce from Thai cooking instructor Kasma Loha-unchit involves making a puree with garlic, shallots, lemongrass, galangal and cilantro roots. This puree includes a touch of shrimp paste and spices like coriander seeds, cumin seeds, nutmeg, cinnamon and mace. The recipe is available at Ruhlman.com.
A recipe from "Southeast Asian Flavors: Adventures in Cooking the Foods of Thailand, Vietnam, Malaysia & Singapore" suggests that cooks simplify the process by using store-bought red curry paste instead of assembling and blending the chilies, vegetables, shrimp paste, herbs and spices themselves.