In a large bowl, whisk together coconut milk, lime juice, soy sauce, chili-garlic sauce, fish sauce, light brown sugar, and freshly grated ginger until combined. Add chicken thighs, cover and marinate for at least 30 minutes.

While marinating, slice Napa cabbage, red cabbage, carrots, and scallions. In a bowl, mix vegetables. In another bowl, combine mayonnaise, sriracha, honey, rice vinegar, and fish sauce. Drizzle over slaw and toss together.

In a shallow dish, whisk together flour, baking powder, ground coriander, and kosher salt. Dredge marinated chicken thighs in the flour mixture.

Heat vegetable oil in a skillet to 350°F. Add coated chicken thighs and cook for about 5-7 minutes per side until golden brown and crispy. Check internal temperature reaches 165°F.

Spread spicy mayonnaise on the bottom half of each bun, add a piece of fried chicken, a scoop of slaw, and pickled cucumber slices. Place the top half of the bun on the sandwich.