Pat the chicken thigh cubes dry with paper towels and place them in a large mixing bowl.
Add the Greek yogurt, ginger-garlic paste, lemon juice, Kashmiri red chili powder, garam masala, ground coriander, ground cumin, turmeric powder, salt, and oil to the bowl.
Mix thoroughly until every piece of chicken is evenly coated in the marinade.
Cover the bowl tightly and refrigerate for at least 2 hours. For the best flavor and texture, marinate overnight.
Soak wooden skewers in water for 30 minutes prior to cooking to prevent them from burning on the grill.
Thread the marinated chicken cubes onto the skewers, alternating with chunks of red onion and green bell pepper.
Preheat a grill to medium-high heat or an oven to 400°F (200°C).
Grill or bake the skewers for 15 to 20 minutes, turning them every 5 minutes, until the chicken reaches an internal temperature of 165°F (74°C) and develops a slight char.
Remove from the heat and let the skewers rest for 5 minutes.
Serve hot with fresh lemon wedges, mint chutney, and warm naan bread.