You may tenderize the meat with Meat tenderizer, meat tenderizer powder, or baking soda. The BEST way that I recently tested is to add some coconut milk and marinate for overnight. You can use any kinds of your favorite marinate sauce. This is what I like and homemade easy!
Adapted from aohmc.blogspot.com
lb. chicken tights, boneless and skinless (about 10-12 pcs.)
cup soy sauce
cup brown sugar
can of coconut milk
some chopped green onion, minced garlic and ginger
Hot pepper paste, if you like spicy
Combine all ingredients together and storage in a covered container. Refrigerate and marinate at least over night. Grill them on a outdoor or indoor grill pan next day.