In a bowl, combine coconut milk, curry powder, minced garlic, grated ginger, salt, and sugar until well blended. Add the chicken thighs, coat them, cover, and refrigerate for at least one hour.

Mix rice flour (or cornstarch) with a pinch of salt and pepper. Dredge each marinated chicken thigh in the flour mixture and set aside on a wire rack.

Heat vegetable oil in a deep pan or skillet to 350°F (175°C). Fry the chicken for 5-7 minutes on each side until golden brown and crispy.

In a mixing bowl, whisk together the Thai chili sauce and mayonnaise or Greek yogurt until smooth. Adjust spice level as desired.

Spread spicy mayo on toasted buns, layer with fried chicken, vegetable slices, and fresh herbs. Press the top bun and serve.

Consider topping with extra herbs or sesame seeds for added flavor and crunch before serving.