Make the chicken and marinade: Cut the chicken lengthwise into 1/4-inch-thick slices, and season them with salt and pepper.
In a blender, blend together the coconut, the gingerroot, the curry powder, the lime juice, and the hot water until the mixture is smooth, strain the mixture through a fine sieve into a bowl, pressing hard on the solids, and let the marinade cool. The marinade may be made 2 days in advance and kept covered and chilled.
In a large shallow dish, pour the marinade over the chicken, coating the chicken well, and let the chicken marinate, covered and chilled, for at least 1 hour and up to 3 hours. (Do not let the chicken marinate longer or the meat will break down.)
Soak the bamboo skewers in water to cover for 15 minutes. Thread the chicken onto the skewers.
Make the sauce: In a saucepan heat oil over moderate heat until hot but not smoking and cook scallions, garlic and ginger, stirring, until fragrant, about 1 minute. Stir in remaining ingredients and bring to a simmer, stirring. Simmer sauce, stirring, until smooth and cool to room temperature. Sauce may be made up to 3 days ahead and chilled, covered. If sauce is too thick after chilling, stir in 1 to 2 tablespoons hot water until sauce reaches desired consistency.
Grill the chicken with the marinade clinging to it on an oiled rack set 5 to 6 inches over glowing coals for 1 1/2 minutes on each side, or until it is cooked through, and serve the sates with the dipping sauce.