Marinate chicken: In a large bowl, combine olive oil, lemon juice, garlic, oregano, thyme, salt, and pepper. Add the chicken cubes and toss to coat. Cover and refrigerate for 2-4 hours, or overnight.

Cook chicken: Thread the marinated chicken cubes onto skewers. Grill or cook the skewers over medium-high heat for 15-20 minutes, or until cooked through and slightly charred.

Assemble souvlaki: Slice the pita bread open and fill with lettuce, tomatoes, red onion, and cooked chicken.

Serve: Serve with tzatziki sauce.

Enjoy your flavorful chicken souvlaki!

Optional toppings: You can also add other toppings to your souvlaki, such as hummus, feta cheese, or pickled red onions.