Place your clean chicken thighs in a gallon size ziplock bag and set it aside.
Now add your sriracha ketchup, brown sugar, soy sauce, garlic powder, onion powder, salt, pepper, and red pepper flakes to a bowl and use a spoon or a whisk and mix it up until everything is fully combined.
Pour all but 1/4 cup of the mixture over the chicken in the ziplock bag. Remove any of the air and zip the bag up tight. Use your hands to massage the marinade into the chicken until every piece is coated.
Place the chicken in the refrigerator for at least one hour, or overnight for the best flavor!
Grill the chicken thighs over medium heat on the stove, or over a 350°F charcoal grill for about 7-10 minutes per side, or until the internal temperature reaches 165°F and the juices run clear.
Remove the chicken from the heat and add the reserved glaze right over the top of the hot chicken. Now, let it rest for at least 5 minutes before cutting into it to serve. And enjoy!