Cut pineapple into 1/2 inch slices and set aside. Trim fat from pork chops, sprinkle lightly with salt and pepper.
Place chops on the rack of a covered grill over medium heat for 4 minutes. Turn chops and add pineapple to the grill. Brush chops with 1 tablespoon marmalade. Grill for 3-5 more minutes or until the pork is no longer pink in the middle, turning pineapple halfway through grilling.
Meanwhile, in a small bowl, combine yogurt and remaining 2 tablespoons marmalade.
Arrange pineapple and pork chops on plates. Sprinkle with fresh thyme and serve with yogurt mixture.