Cut the chicken thighs into 1/2-wide long strips and place into a large resealable bag. In a bowl, whisk together the chili sauce, pineapple juice, soy sauce, and garlic. Pour the marinade into the bag over the sliced chicken. Seal the bag and toss to coat completely. Place the bag into a large bowl and put into the refrigerator to marinate for at least 1 hour or as long as overnight.
To serve: Preheat a grill or grill pan over medium-high heat. Thread the chicken strips onto the skewers. Oil the grill gates and place the chicken on the grill. Cook until the chicken is just cooked through, 4 to 5 minutes per side. Remove from the heat and serve immediately.