Preheat the oven to 400°F (200°C) and spray a 9x13-inch baking dish with cooking spray.
Pat the chicken thighs dry with paper towels and place them nearby.
In a large bowl, whisk together 1/4 cup white miso paste, 2 tablespoons rice vinegar, 2 tablespoons honey, 1 tablespoon garlic (paste or grated), 1 tablespoon soy sauce, and 1 teaspoon ginger (paste or grated) until smooth.
Add the chicken thighs to the bowl and rub the miso mixture over each piece to coat evenly; let them marinate for 10 minutes.
Arrange the chicken thighs skin side up in the prepared baking dish, leaving space between pieces.
Brush any remaining miso mixture over the tops of the thighs.
Bake for 35–40 minutes, or until the internal temperature of the chicken reaches 165°F (74°C) and the skin is golden.
Remove from the oven and let the chicken rest for a few minutes before serving.