Preheat oven to 425ºF (220ºC).
In food processor or plastic bag, crush melba toasts until in coarse crumbs; transfer to bowl.
Add butter; toss to combine.
In small bowl, whisk together mayonnaise, mustard, thyme, salt and pepper; spread over chicken.
Dip into crumb mixture, turning and pressing to coat.
Place chicken on rack on rimmed baking sheet; bake in oven for about 35 minutes or until golden and juices run clear when chicken is pierced.