In a mixing bowl, whisk together peanut butter, soy sauce, honey, rice vinegar or lime juice, sesame oil, minced garlic, grated ginger, chili flakes or Sriracha, and water or chicken broth until smooth. Add coconut milk if using. Sauce should have pancake batter consistency.
Place chicken pieces at the bottom of your slow cooker in a single layer. Pour the prepared peanut sauce over the top, making sure every piece is well coated.
Cover and cook on low for 5-6 hours or on high for 2.5-3.5 hours until chicken is tender and reaches 165°F internal temperature. Chicken should shred easily when done.
Use two forks to shred the chicken directly in the slow cooker. Stir everything together so the shredded chicken absorbs all the peanut sauce. If sauce is too thin, cook uncovered on high for 15-20 minutes. If too thick, add 2-3 tablespoons water or coconut milk.
Taste and adjust seasonings if needed, being cautious with salt as soy sauce is salty. Garnish generously with crushed peanuts, chopped cilantro, sliced green onions, and sesame seeds before serving hot.
Notes
Use chicken thighs for juiciest results. They stay more tender during long cooking time compared to breasts.
For nut-free version, substitute peanut butter with sunflower seed butter or tahini in equal amounts.
Sauce thickens when refrigerated and oil may separate. Add splash of water or coconut milk when reheating leftovers.
Coconut milk is optional but highly recommended for extra creaminess and authentic Thai flavor.