Heat the oven to 200C/180C fan/gas 6. Slice the pitta into triangles, put on a baking sheet and drizzle over the oil. Bake for 10-15 mins until golden and crisp.
Mix together the Tabasco, ketchup, mayo, yogurt and lime zest and juice. Toss the prawns in the dressing.
Layer the lettuce, cucumber, tomatoes and dressed prawns in a lunchbox or jar. Season, top with the pitta chips and serve with lime wedges.