In a large bowl, combine soy sauce, vinegar, minced garlic, bay leaves, peppercorns, and brown sugar. Whisk until sugar dissolves.

Add chicken thighs to the marinade, turning to coat. Cover and refrigerate for at least 30 minutes (or overnight for deeper flavor).

Heat 2 tablespoons vegetable oil in a large skillet over medium-high heat. Cook chicken, skin-side down, until golden brown (2–3 minutes per side). Transfer to a plate and set aside.

Carefully pour the marinade into the same skillet. Bring to a simmer, scraping up any browned bits from the bottom.

Return the chicken to the skillet, reduce heat to medium-low, cover, and simmer for 30–35 minutes, flipping once, until the sauce thickens slightly and chicken is cooked through.

Adjust seasoning with salt and pepper. Remove bay leaves before serving.

Serve hot over steamed rice and spoon extra sauce on top.