Preheat the oven to 400 degrees F (200 degrees C).

Combine chicken and 4 ounces enchilada sauce in a bowl; toss to combine. Transfer onto a baking sheet.

Bake in the preheated oven for 20 minutes.

Remove baking sheet from the oven and drain liquid. Baste remaining enchilada sauce over chicken thighs and return to the oven. Continue baking until chicken is no longer pink in the center and the juices run clear, about 10 more minutes. Remove from oven and divide Cheddar cheese and olives evenly on top of the chicken.

Set an oven rack about 6 inches from the heat source and preheat the oven's broiler. Broil chicken until cheese is melted, about 5 minutes. Garnish with green onions, sour cream, and cilantro.