In a large bowl, whisk together coconut milk, curry powder, minced garlic, grated ginger, salt, and sugar until well combined. Add the chicken thighs, ensuring they are thoroughly coated in the marinade. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, or up to overnight for maximum flavor and tenderness.

On a large plate, combine rice flour or cornstarch with a pinch of salt and pepper. Take the marinated chicken out of the fridge and one by one, dredge each thigh in the flour mixture, ensuring an even coating that will create a delightful crispness. Shake off any excess flour before moving on to the next step.

In a deep skillet or fryer, pour in enough oil to reach about 2 inches deep, then heat the oil to 350°F (175°C) over medium-high heat.

Carefully place the coated chicken thighs into the hot oil in batches, avoiding overcrowding. Fry for about 5-7 minutes on each side, or until they are golden brown.

While the chicken is frying, prepare the spicy spread by whisking together the Thai chili sauce and plain yogurt in a small bowl until well combined.

Lightly toast both halves of the brioche or sandwich buns in a toaster or on a skillet until they are golden and slightly crisp.

Spread a generous amount of the Thai chili mayo on the bottom half of each toasted bun. Layer in the crispy fried chicken thighs, followed by fresh cucumber slices, pickled carrots, and any other desired toppings, such as fresh herbs.

For an extra burst of flavor, finish your sandwich with a sprinkle of fresh cilantro, a squeeze of lime, or some crushed peanuts.