Combine minced lemongrass, garlic, ginger, fish sauce, soy sauce, sugar, lime juice, oil, pepper, and cornstarch. Mix thoroughly so flavors distribute evenly. The marinade should smell fragrant and balanced.
Add chicken thighs to marinade and coat thoroughly. Cover and refrigerate at least 30 minutes, or overnight for deeper flavor. Longer marination results in juicier, tastier chicken.
Preheat air fryer to 380°F (193°C) for even cooking. Lightly oil basket if needed to prevent sticking. Proper preheating ensures crisp exterior.
Arrange chicken in a single layer without overcrowding. Cook 12–15 minutes, flipping halfway for even browning. Chicken should be caramelized outside and juicy inside.
Let chicken rest for a few minutes after cooking. This keeps juices inside the meat. Resting improves texture and flavor.
Slice chicken and garnish with herbs or green onions. Serve immediately while hot and fragrant. Fresh lime wedges enhance flavor.