In a mixing bowl, combine Greek yogurt, olive oil, lemon juice, minced garlic, oregano, cumin, smoked paprika, salt, and pepper. Add the chicken thighs and coat them thoroughly. Cover and refrigerate for at least 30 minutes to allow the flavors to meld.
Heat a large skillet over medium heat. Once hot, add the marinated chicken thighs. Cook for about 7-8 minutes on each side, or until the chicken is cooked through and has a golden-brown color. Remove chicken from the skillet and let it rest for a few minutes before slicing.
In the same skillet, add the diced cucumber, tomato, and sliced red onion. Season with salt and pepper, and sauté for 3-4 minutes until they are slightly softened but still crisp.
While the vegetables are cooking, separately warm the whole wheat pita breads in a dry pan or microwave them for about 15-20 seconds until they are soft and pliable.
To assemble, slice the rested chicken thighs into strips. Take a warm pita, add a generous scoop of the sautéed vegetables, and top with the sliced chicken. For an extra touch, sprinkle crumbled feta cheese and chopped parsley on top.
Serve immediately with extra Greek yogurt on the side for dipping or drizzling over the top.
Notes
For extra flavor, let the chicken marinate longer if possible.