Preheat oven to 400°F. Line a rimmed baking sheet with foil. Set wire rack on sheet and mist with nonstick cooking spray.
Combine cornflakes, salt, garlic powder, onion powder, paprika, thyme and 1/4 cup mayonnaise in a medium bowl. Stir until mixture is crumbly.
Coat each drumstick with 1/2 Tbsp. mayonnaise, then coat with crumb mixture. Place on prepared rack. Bake until chicken is golden and an instant-read thermometer inserted into leg registers 165°F, about 30 minutes, tenting with foil if legs begin browning too quickly. Remove baking sheet from oven and let chicken rest for 10 minutes. Wrap bone end of each drumstick with aluminum foil and serve.