Marinate the Chicken: In a bowl, combine the diced chicken with red curry paste, fish sauce, salt, turmeric, and sugar.
Mix everything thoroughly to coat the chicken.
Cover the bowl and let the chicken marinate for at least 30 minutes, or up to 24 hours for better flavor.
Soak wooden skewers in water for at least 30 minutes before you plan to grill them.
Make the Sauce: In a small saucepan over medium heat, combine peanut butter, water, coconut milk, red curry paste, soy sauce, fish sauce, and sugar.
Whisk the ingredients until smooth and fully combined.
Cook the sauce for 3-4 minutes, or until it reaches a pourable consistency. If the sauce is too thick, add a little water to adjust the consistency.
Cook the Chicken: Thread the marinated chicken pieces onto soaked wooden skewers.
Preheat a grill pan or outdoor grill to medium-high heat. If using a grill pan, add oil to the pan. If using an outdoor grill, clean and lightly oil the grill grates.
Place the chicken skewers on the preheated grill or pan.
Cook for 3-4 minutes on each side, or until the chicken reaches an internal temperature of 165°F (74°C).
Serve the cooked chicken skewers with the prepared peanut sauce. Garnish with chopped cilantro, crushed peanuts, and sliced red onion, if desired.