Whisk the soy sauce, balsamic vinegar, honey, crushed garlic, Sriracha, and grated ginger together in a small bowl until combined.
Reserve half of the marinade (about 1/4 cup) by pouring it into a small saucepan; set aside for later reduction.
Place the chicken thighs in a large bowl and add the remaining marinade, turning to coat all pieces. Cover and refrigerate for at least 2 hours or up to overnight.
Preheat the air fryer to 400°F (204°C).
Remove chicken from the marinade, letting excess drip off, and arrange in a single layer in the air fryer basket (cook in batches if needed).
Air fry the chicken for 14 minutes, flipping once halfway through, until an instant-read thermometer inserted in the thickest part reads 165°F (74°C).
While the chicken cooks, place the reserved marinade in the saucepan and simmer over medium-low heat for 1–2 minutes until it reduces slightly and thickens into a glaze.
Drizzle the reduced glaze over the cooked chicken and sprinkle with sliced scallion greens before serving.
