In a small bowl, whisk together 1/4 cup lemongrass powder, 1/4 cup olive oil, 1/4 cup soy sauce, 1/4 cup lime juice, 2 tablespoons Worcestershire sauce, 1 teaspoon garlic salt, and 1 teaspoon lemon pepper until smooth and combined.
Place 4 bone-in, skin-on chicken thighs into a large resealable plastic bag and pour the marinade over the chicken.
Seal the bag, pressing out as much air as possible, then massage the marinade over the chicken so it is evenly coated.
Refrigerate and marinate for 30–60 minutes (or up to 24 hours if desired).
Preheat the air fryer to 350°F (175°C).
Place the marinated chicken thighs skin-side down in the air fryer basket in a single layer, then cook for 10 minutes.
Flip the thighs and cook an additional 7–8 minutes, or until an instant-read thermometer inserted into the thickest part reads 165°F (74°C).
Remove the chicken and let rest for 5 minutes before serving. Garnish with minced fresh scallions if desired.