In a large bowl, whisk together coconut milk, curry powder, minced garlic, grated ginger, salt, and sugar until blended. Submerge the chicken thighs in the marinade and cover. Refrigerate for at least 1 hour or overnight.

Mix rice flour or cornstarch with a pinch of salt and pepper in a shallow dish. Remove the marinated chicken, allowing excess marinade to drip off, and dredge each piece in the flour mixture.

Heat oil in a deep skillet over medium-high until it reaches 350°F (175°C). Fry chicken for 5-7 minutes per side until golden brown and cooked through. Drain on a wire rack.

In a mixing bowl, combine Thai chili sauce and plain yogurt, whisking until smooth. Adjust heat to taste by adding more chili sauce.

Toast the buns, spread the Thai chili sauce mixture, stack fried chicken, and top with cucumber slices and pickled carrots. Garnish with fresh herbs or peanuts if desired.

Serve immediately with sides like sweet potato fries or store components separately for best freshness when reheating.