Marinate chicken: combine chicken thighs with soy sauce, vinegar, garlic, bay leaves, peppercorns, and sugar; let rest 15 minutes.
Heat oil in a pot over medium heat and brown chicken on all sides; remove and reserve.
Add marinade and water to the pot and bring to a boil.
Return chicken to the pot, cover, and simmer until sauce thickens and chicken is cooked through, about 25 minutes.
Garnish with sliced green onion and serve over rice.