In a bowl, combine the buttermilk and hot sauce. Add the chicken thighs, ensuring they are submerged in the mixture. Cover and refrigerate for at least 2 hours (or overnight for best flavor).
In another bowl, whisk together the flour, cayenne pepper, paprika, garlic powder, onion powder, salt, and pepper.
Remove the marinated chicken from the refrigerator. Take each thigh and dredge it in the seasoned flour mixture, ensuring an even coat. Shake off any excess flour.
In a large skillet or deep fryer, heat oil to 180°C (350°F). Carefully place the coated chicken thighs in the hot oil and fry for about 6-8 minutes on each side, or until golden brown and cooked through. Use a meat thermometer to ensure they reach an internal temperature of 75°C (165°F).
In a small bowl, mix the mayonnaise with the sriracha sauce to create a spicy mayo.
Toast the burger buns lightly, then spread a generous amount of spicy mayo on the bottom half of each bun. Add lettuce, a slice of fried chicken, tomato, avocado, and pickles. Top with the other half of the bun.
Enjoy your Spicy Zinger Chicken Burger immediately while it's hot and crispy!