Whisk the vinegar, honey, soy sauce, toasted sesame oil, chili garlic sauce, garlic, and salt in a bowl until smooth. Pour half the marinade into a large plastic zipper bag; retain the other half of the sauce. Place the chicken thighs into the bag containing marinade, squeeze all the air out of the bag, and seal. Shake a few times to coat chicken; refrigerate for 1 hour, turning bag once or twice.
Preheat oven to 425 degrees F (220 degrees C).
Pour the other half of the marinade into a saucepan over medium heat, bring to a boil, and cook for 3 to 5 minutes, stirring often, to thicken sauce. Remove the chicken from the bag; discard used marinade. Place chicken thighs into a 9x13-inch baking dish, and brush with 1/3 of the thickened marinade from the saucepan.
Bake 30 minutes, basting one more time after 10 minutes; an instant-read thermometer inserted into a chicken thigh should read 165 degrees F (75 degrees C). Let stand for 5 or 10 minutes; meanwhile, bring remaining marinade back to a boil for 1 or 2 minutes, and serve chicken with marinade. Sprinkle with green onions.