Like all my chicken grilling recipes, this recipe calls for basting at the end of grilling. That's especially important in this case because the sugar in the glaze will burn easily if you apply it any sooner. Also, don't increase the chili-garlic sauce amount. It is very potent.
In a large bowl, combine water and soy sauce in large bowl. Set aside. In a large skillet, heat oil over medium-high heat until shimmering. Add garlic and ginger and cook until fragrant, about 30 seconds. Stir into water/soy sauce mixture. Add chicken and refrigerate, covered, for at least 1 hour and up to 8 hours. Go for the full 8 hours if at all possible, but no more than that or the chicken will get too salty.
In a medium sauce pan, combine the pineapple juice, sugar, soy sauce, ketchup, vinegar, garlic, ginger, and chili-garlic sauce. Bring to a boil then reduce heat to medium and let simmer until glaze is thick and syrupy about 20 to 25 minutes. This should result in about 3 cups of glaze.
Remove chicken from brine and pat dry with paper towels. Arrange chicken skin-side up on grill. Grill, covered, until chicken is well browned on bottom and meat registers 120 degrees, about 25 to 30 minutes. Flip chicken skin-side down and continue to grill, covered, until skin is well browned and crisp and meat registers 170 to 175 degrees, 20 to 25 minutes longer. Apply glaze several minutes before removing chicken from grill.
You can make the chicken to this point up to 2 hours before serving. Transfer to a large disposable aluminum serving tray, cover with foil and hold in a 200 degree (warm) oven.
NOTE: Do not exceed approximately 36 - 40 thighs on a standard size gas grill. Many more than that and they will render so much fat that you can easily have a grill fire. Not good.