In a large mixing bowl, combine coconut milk, curry powder, minced garlic, grated ginger, salt, and sugar, whisking until smooth. Add chicken thighs to the marinade, ensuring they are fully coated. Cover with plastic wrap and refrigerate for at least 1 hour or up to overnight.

Set up your dredging station. On a large plate, mix rice flour or cornstarch with a pinch of salt and pepper.

Remove the chicken thighs from the marinade and dredge each piece in the prepared dry mix, pressing down to ensure an even coating.

In a deep skillet, pour enough vegetable oil to reach a depth of about 2 inches. Heat the oil over medium-high heat until it reaches 350°F (175°C).

Carefully lower the coated chicken thighs into the hot oil, frying for 5-7 minutes on each side until golden brown and an internal thermometer reads 165°F (74°C).

In a small mixing bowl, whisk together Thai chili sauce and plain yogurt until smooth and creamy. Adjust spice levels as desired.

Toast your brioche or sandwich buns until golden brown. Spread spicy mayo on both halves, layer the fried chicken, cucumbers, pickled carrots, and fresh herbs, and top with the other half of the bun.