In a large mixing bowl, whisk together the coconut milk, Thai red curry paste, fish sauce, brown sugar, and fresh lime juice until the marinade is smooth and well combined.

Add the cubed chicken thighs to the bowl, tossing well to ensure every piece is thoroughly coated in the red curry mixture. Let sit for at least 15 minutes at room temperature to absorb the flavors.

While the chicken marinates, prepare your skewers. If using wooden skewers, soak them in water for at least 20 minutes to prevent them from burning during cooking.

Thread the marinated chicken onto the skewers, alternating with pieces of red bell pepper and red onion. Leave a small amount of space between the pieces so the heat can circulate and cook the meat evenly.

Preheat your grill or a large cast-iron grill pan over medium-high heat. Once hot, lightly brush the grates with vegetable oil to prevent sticking.

Place the kebabs on the hot grill and cook for 12 to 15 minutes, turning every 3 to 4 minutes. The chicken is done when it is opaque throughout, has beautiful charred marks, and reaches an internal temperature of 165°F (74°C).

Remove the chicken kebabs from the grill and let them rest for 3 minutes to lock in the juices. Sprinkle with fresh chopped cilantro and serve immediately with steamed rice and a squeeze of fresh lime.