Preheat the air fryer to 400°F (200°C) for 5 minutes.
In a small bowl, combine smoked paprika, garlic powder, onion powder, salt, and black pepper.
Pat the chicken thighs dry with paper towels and rub olive oil evenly over both sides.
Sprinkle the seasoning mixture evenly over both sides of the chicken thighs.
Place the seasoned chicken thighs in the air fryer basket in a single layer.
Cook the chicken thighs in the air fryer at 400°F (200°C) for 18-20 minutes, flipping halfway through, until the internal temperature reaches 165°F (74°C) and the outside is crispy.
While the chicken cooks, slice the sandwich buns in half and toast them lightly in a toaster or on a skillet.
Spread 1 tablespoon of mayonnaise on the bottom half of each toasted bun.
Place one leaf of romaine lettuce and one slice of tomato on the bottom half of each bun.
When the chicken thighs are done, let them rest for 2 minutes, then place one chicken thigh on top of the tomato on each sandwich.
Cover with the top half of the buns and serve immediately.