If using bamboo skewers, soak them in water for at least 30 minutes. If using metal, no need to soak.
Add marinade ingredients, except chicken, to a large mixing bowl. Whisk well, then stir in chicken pieces. Cover and refrigerate for at least 30 minutes, or up to overnight.
Add all peanut sauce ingredients to a small mixing bowl and whisk well to combine. Sauce should be thick, but still a pourable sauce. If sauce is too thick, add some warm water, a little at a time, whisking after each addition, until desired consistency is reached. Set aside.
Thread marinated chicken pieces onto skewers and add the skewers to a wax paper lined baking sheet (for transport to the grill).
Brush grill grates with vegetable oil and preheat grill over MED HIGH heat.
When the grill is hot, add skewers to the grill, close the lid, and cook 8-10 minutes, flipping once or twice during cooking. Chicken should be golden brown with a little char, and be cooked through.
Add cooked skewers to a platter, and sprinkle them with cilantro, Thai chiles and some chopped peanuts. Serve a bowl of the sauce, also topped with a little chopped peanuts and sliced chiles, so the skewers can be dipped in the sauce before eating. Sauce may also be drizzled over the skewers.
