Prepare the tamarind paste by mixing ¼ cup wet tamarind block with ½ cup water. Mash with your fingers until a thick paste is formed, then strain to remove the seeds and veins.
Prepare the toasted rice powder by slowly toasting ¼-1/2 cup of Thai sticky rice over low heat until it is rich, golden brown in color and has a toasted aroma. Grind into a powder using a mortar and pestle or coffee/spice grinder.
Slice the shallots into small, thin pieces and coarsely chop the cilantro.
Mix the tamarind paste, water, fish sauce, and palm sugar in a bowl. Continue mixing until the palm sugar is completely incorporated into the liquid. Add the rest of the ingredients. Taste and adjust the flavors according to your preferences. The primary flavors should be sour, spicy, and salty.