In a small bowl stir together the mayonnaise, curry powder, lemon zest, lemon juice and soy sauce until combined.
In a large mixing bowl stir together chicken, water chestnuts, grapes, celery and mayonnaise mixture. Season with salt and pepper then gently mix in the melon balls and almonds.
Cover with plastic wrap and refrigerate until ready to serve. Let stand at room temperature for 20 minutes before serving.