1. In a mixing bowl, combine olive oil, lemon juice, minced garlic, ground cumin, ground coriander, paprika, ground turmeric, salt, and black pepper. Mix well.
2. Add chicken thighs to the bowl and coat them well with the marinade. Let it marinate for at least 1 hour or overnight in the refrigerator.
3. Preheat the grill to medium-high heat. Grill the marinated chicken thighs for about 5-7 minutes on each side or until fully cooked.
4. Once cooked, let the chicken rest for a few minutes before slicing it into thin strips.
5. Warm the pita bread on the grill for a minute or two.
6. In a small bowl, mix yogurt, diced cucumber, sliced red onion, and chopped parsley to make the sauce.
7. Assemble the sandwiches by placing the sliced chicken on the warm pita bread and topping it with the yogurt sauce. Serve immediately.