In a large bowl, combine the vinegar, soy sauce, garlic, peppercorns, bay leaves, and brown sugar. Add the chicken and toss to coat. Cover the bowl and place it in the refrigerator for at least one hour, and up to three hours.
Heat the oil in a large skillet over medium-high heat. Once the oil is glistening, working in batches, add the chicken thighs (reserving the marinade in the bowl) in a single layer. Cook, undisturbed, until the chicken begins to brown on the bottom, about 4 minutes. Flip the chicken and repeat on the other side, about another 4 minutes.
Add the remaining marinade to the skillet and bring to a boil. Lower the heat to medium/medium-low to maintain a heavy simmer for 10 minutes. Flip the chicken thighs. Simmer, stirring occasionally, until the sauce has reduced by half and is beginning to thicken, about 10 more minutes. When the chicken thighs reach 165°F on an instant-read thermometer, remove from the heat.
Serve the chicken thighs over cooked rice, sprinkled with green onions.