In a deep-fryer or heavy-bottomed pot, heat enough oil to come halfway up the sides of the pot, to 350 degrees F.
In a small bowl, mix together salt, chili powder, smoked paprika, garlic powder, and black pepper.
Using a mandoline or a sharp knife, thinly slice the sweet potatoes into 1/8-inch thick rounds. Add the sliced sweet potatoes to the hot oil and fry, in batches, until crisp and golden brown, about 3 minutes. Remove to a paper towel lined sheet tray and immediately sprinkle with the seasoning mixture. Transfer to a serving bowl and serve.