In a large bowl, whisk together soy sauce, water, brown sugar, onions, garlic, sesame oil, and coconut milk. (Reserve some green onions for garnish.) Add the chicken to the bowl or transfer to a bag or container of your preference, cover and marinate for at least 8 hours or overnight.
To prepare the rice, replace half of the water called for with canned coconut milk and cook the rice according to the directions on the rice packaging.
Grill chicken on a low heat so the marinade does not burn, about 5-7 minutes per side or until done. Cooking time will vary depending on the size of the thighs, so a meat thermometer comes in handy - safe internal temperature is 165 degrees F.
Serve over rice and garnish with green onions.
Notes
Use Aloha Shoyu soy sauce or a low-sodium soy sauce.