Preheat the oven to 400°F. Line a baking sheet with parchment paper.
In a large bowl, combine the olive oil, garlic powder, onion powder, dried thyme, salt, and black pepper. Add the sweet potato slices and toss until they are evenly coated with the oil mixture.
Stack the sweet potato slices in a circular pattern on the prepared baking sheet, creating small stacks. Sprinkle the grated Parmesan cheese generously over each stack.
Bake in the preheated oven for 25-30 minutes, or until the sweet potatoes are tender and the cheese is golden brown and crispy. For extra crispiness, broil for an additional 2-3 minutes, watching closely to prevent burning.
Remove from the oven and let cool for a few minutes. Garnish with fresh thyme leaves if desired before serving.