Thinly slice chicken. Season with garlic powder, salt and pepper. Add to a resealable bag.
In a mason jar or container mix together coconut milk, pineapple juice, soy sauce, brown sugar, minced garlic and ginger.
Pour half of the mixture over chicken. Refrigerate for at least 30 minutes, or overnight. The longer the better.
Reserve remaining marinade for cooking.
Heat about 1 tablespoon oil in a large skillet or wok over medium high heat. Remove chicken from marinade and add to skillet. Cook chicken, stirring occasionally until almost cooked. Use a baster to remove any excess liquid if it begins to pool. You want the chicken to cook nice.
Once the chicken is almost cooked add in vegetable mixture and pineapple chunks. Season with salt. Cook, stirring occasionally until the vegetables are heated through. Use a baster again to remove liquid that pools from vegetables when cooking.
Mix 1 tablespoons cornstarch with reserved marinade until dissolved. Pour over chicken and vegetables and stir to coat. Let cook for a few minutes until sauce thickens.
Remove from heat, season with additional salt to taste. Serve over rice if desired.