My Thai peanut sauce is a little bit different every time. It always consists of a little bit of this and a little bit of that until it tastes just right and I have the amount of it that I need. For the purposes of getting the recipe down here, though, I've pinned down the essential ingredients in approximate amounts, but you should feel free to adjust to your liking.
Most peanut sauces have fewer ingredients, some with just peanut butter, soy sauce, rice vinegar, and water. I think that the three essentials of Thai cooking are basil, garlic, and ginger, and so these get included in my sauce, along with lots of red pepper flakes and hot sauce for spice. Regardless of how you like yours, this is an incredibly satisfying and delicious sauce that is versatile for dipping or pouring over rice or noodles.
Spicy Thai Peanut Sauce
1/4 cup smooth honey roasted peanut butter (not natural)
1/8 cup reduced sodium soy sauce1/8 cup milk, coconut milk, or water
2 T. rice vinegar
1 T. sesame oil
1 T. hot sauce or chili paste
2 t. garlic powder or one fresh garlic clove, minced and pressed into a paste
2 t. dried basil or 1 T. fresh
2 t. curry powder
1 t. Chinese Five Spice
1/2 t. ginger powder
2 t. crushed red pepper flakes
1/4 of a lemon, freshly squeezed (you may want to wait to squeeze the lemon over the dish you're serving with the sauce so that the milk does not curdle. If you have used water, feel free to mix the lemon in)
Whisk ingredients together until well blended, or use a processor to blend. Adjust to taste.
If you don't have all of the above spices or ingredients, don't worry. You can substitute regular white or cider vinegar for the rice vinegar, and pumpkin or apple pie spice for the Chinese five spice, etc.
A well stocked spice cabinet is the most useful way to add flavor to a dish though, so definitely keep your eyes peeled for a good spice store nearby and start collecting!