Prepare the Marinade: In a large mixing bowl, whisk soy sauce, brown sugar, ketchup, pineapple juice, ginger, and garlic. Whisk until the sugar is completely dissolved.

Marinate the Chicken: Place the chicken thighs in a large resealable plastic bag or a shallow dish. Pour 1½ cups of the marinade over the chicken, reserving the remaining for basting. Seal the bag or cover the dish, and refrigerate for at least 4 hours or up to overnight.

Preheat: Preheat your smoker to 250°F and add wood pellets if needed. I used cherry wood pellets.

Smoke the Chicken: Remove the chicken from the marinade, letting any excess drip off. Discard the used marinade. Arrange the chicken thighs on the smoker grates, skin side up. Smoke chicken for 1½ to 2 hours, flipping and basting with the reserved marinade every 30 minutes, until the internal temperature of the chicken reaches 175°F.

Thicken the Reserved Marinade: While the chicken is smoking, take the remaining ½ cup of the reserved marinade and bring it to a simmer in a small saucepan. Mix 1 tablespoon of cornstarch with 1 tablespoon of cold water in a small bowl to create a slurry. Gradually add the slurry to the simmering marinade, whisking constantly until thickened. This will be your serving sauce. Remove from the heat and cover to keep warm.

Garnish and Serve: Remove the chicken from the smoker and let it rest for a few minutes before serving. Enjoy!