In one bowl, mix the flour, cornstarch, paprika, garlic powder, cayenne pepper, salt, and pepper to create a batter.
In another bowl, pour the buttermilk.
Dip each shrimp into the buttermilk, allowing excess to drip off, then coat with the flour mixture. Set aside.
Heat oil in a large skillet over medium-high heat. Fry the shrimp in batches until golden brown and crispy, about 2-3 minutes per side. Remove and drain on paper towels.
In a mixing bowl, gently toss the cooked shrimp with the Thai sweet chili sauce until well coated.
Warm the tortillas in a skillet or microwave until pliable.
To assemble the tacos, place a layer of shredded lettuce on each tortilla, followed by a few avocado slices, and top with the shrimp.
Finish by sprinkling sliced green onions and cilantro over the filled tacos.