Place turkey, chili-garlic sauce, scallions, cilantro, lime zest, and ½ teaspoon salt in medium bowl and mix until combined. Form mixture into eight ¾-inch thick patties.
In small bowl, whisk together peanut butter, 4 tsp fish sauce, 1 tbsp brown sugar, and 3 tbsp lime juice. Season with salt and pepper to taste.
In separate bowl, toss cucumber, onion, 2 tbsp lime juice, 2 tsp fish sauce, 2 tsp brown sugar; season with salt and pepper to taste.
Grill until cooked through, 5 to 7 minutes per side. Serve on buns with peanut sauce and cucumber salad.