Preheat the oven to 400°F. Lightly spray a 9x13x2-inch baking dish with cooking spray and set it aside.
Pat the 8 chicken thighs (bone-in, skin on) dry with paper towels.
In a large bowl, whisk together 1/4 cup white miso paste, 2 tablespoons rice vinegar, 2 tablespoons honey, 1 tablespoon garlic paste, 1 tablespoon soy sauce, and 1 teaspoon ginger paste until smooth.
Scoop out and set aside a small portion of the miso mixture in a separate bowl for glazing later. (This keeps the reserved glaze free from raw chicken.)
Add the chicken thighs to the remaining miso mixture in the large bowl and rub each thigh thoroughly so they are evenly coated. Let the chicken marinate in the bowl for 10 minutes, turning once if needed to coat both sides.
Remove the chicken thighs from the marinade and arrange them skin side up in the prepared baking dish.
Brush the reserved miso mixture over the tops of the chicken thighs, then bake uncovered for 35–40 minutes, or until an instant-read thermometer inserted into the thickest part of the thigh (not touching bone) reads 165°F.
Remove the chicken from the oven and let it rest for a few minutes before serving.