In a large nonreactive sauté pan, whisk together the soy sauce and vinegar until combined.
Add the smashed garlic, whole black peppercorns, and bay leaves to the pan and stir to distribute.
Place the chicken thighs into the pan, skin side down, nestling them into the liquid.
Bring the liquid to a boil over high heat, then reduce the heat to low, cover, and simmer for 15 minutes.
Turn the chicken over, cover again, and simmer on low for another 10 minutes.
Uncover the pan and increase the heat to high to return the sauce to a boil.
Boil the sauce, uncovered, while occasionally turning and basting the chicken, until the sauce has reduced by about half and thickened slightly, about 5 minutes.
Remove from heat and serve the chicken with steamed white rice.