Creamy Chicken and Wild Rice Soup

Name: Creamy Chicken and Wild Rice Soup
Ingredients: 1 medium yellow onion; 2 medium carrots; 2 medium stalks celery; 3 cloves garlic; 3 tablespoons unsalted butter; 3/4 teaspoon dried thyme; 2 dried bay leaves; 1 1/2 teaspoons kosher salt, divided, plus more as needed; 1/4 teaspoon freshly ground black pepper, plus more as needed; 1 cup wild rice (not wild rice blend); 1/3 cup all-purpose flour; 6 cups low-sodium chicken broth; 2 cups whole or 2% milk; 1 pound boneless, skinless chicken thighs (about 4)