In a mixing bowl, combine the coconut milk, lime juice, reduced-sodium soy sauce, chili-garlic sauce, fish sauce, light brown sugar, and minced fresh ginger. Whisk until smooth, then add the skinless, boneless chicken thighs, ensuring they are well-coated. Cover the bowl with plastic wrap and let the chicken marinate in the refrigerator for at least 30 minutes.

In a separate bowl, mix together the all-purpose flour, baking powder, ground coriander, and kosher salt. Set the bowl aside.

Fill a deep saucepan or skillet with vegetable oil, approximately 2 inches deep, and heat it over medium-high heat. Use a thermometer to monitor the temperature, aiming for 350°F (175°C).

Once the oil is hot, carefully remove the chicken thighs from the marinade, dredge them in the flour mixture, and fry for about 5-7 minutes per side until golden brown. Transfer to a plate lined with paper towels.

In a large bowl, combine the napa and red cabbage, carrot, scallions, cilantro, garlic, lime juice, rice vinegar, fish sauce, soy sauce, grated ginger, and toasted sesame oil. Toss until well mixed.

Spread a generous layer of spicy mayo on the bottom bun, place the crispy fried chicken on top, followed by slaw and cucumber or pickles. Finish with the top bun.