Mix together the sweet chilli sauce, cumin seeds, ground coriander and oil in a non-metallic bowl. Add the meat and stir well to coat, then cover and leave to marinate in a cool place for 30 minutes.
Thread the meat on to four bamboo skewers that have been soaked in water for at least 20 minutes. Cook on a hot griddle or under a high grill for 2–3 minutes until cooked through.
Meanwhile, mix together the sauce ingredients in a small serving bowl. Serve the skewers with the sauce, scattered with the coriander and peanuts, if desired.