In a medium bowl, mix peanut butter, spring onions, soy sauce, lemon juice, brown sugar, garlic, coriander and chillies. Add pork, and toss to coat. Cover, and marinate in the refrigerator at least 30 minutes.
Preheat barbecue for high heat.
Thread marinated pork, water chestnuts, capsicums and onion alternately onto skewers. Transfer remaining marinade to a small saucepan, bring to the boil and cook for several minutes.
Lightly oil cooking grate. Cook skewers for 10 minutes, or to desired doneness. Turn skewers while barbecuing to cook evenly, and brush with boiled marinade during last few minutes.