Boil soy sauce, vinegar, water, garlic, ginger bay leaves and pepper flakes in large pot over high heat for the marinade
Add thighs, reduce heat to medium and simmer, partially covered for 15 minutes. Flip thighs.Simmer 15 minutes more. Cool thighs, then cover pot and chill. Preheat grill to medium low. Brush grill grate with oil
Remove thighs from marinade and pat dry with paper towels. Skim off and discard fat from surface of marinade. Boil marinade til reduced to 1 cup. Strain.
Grill thighs til an in stent read thermometer inserted into thickest part registers 145, about 6 to 8 minutes per side. Serve thighs and rice with sauce
For scallion rice, cook 1 cup of dry long grain white rice as pkg. directs. Stir in 1/2 cup sliced scallions and season with rice vinegar and kosher salt.