Step 1

Whisk water, soy sauce, coconut milk, brown sugar, green onions, white onion, sesame oil, and garlic together in a large glass or ceramic bowl. Add chicken thighs and toss to evenly coat. Cover the bowl with plastic wrap and marinate in the refrigerator, 4 hours to overnight.

Step 2

Preheat grill for medium heat and lightly oil the grate.

Step 3

Remove chicken from marinade and discard the marinade.

Step 4

Cook chicken on the preheated grill until no longer pink in the center and the juices run clear, 5 to 7 minutes per side. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).