Marinate the chicken by mixing soy sauce, fish sauce, lime juice, ginger, garlic, coriander, white pepper, and turmeric. Submerge chicken thighs in mixture, refrigerate for at least 2 hours, ideally overnight.

Prepare the pickled slaw by combining shredded cabbage and carrots, mixing rice vinegar, sugar, and salt, and pouring over veggies. Let sit for at least 30 minutes.

For spicy mayo, combine mayonnaise, sriracha, lime juice, honey, and sesame oil in a bowl. Mix until smooth, then refrigerate.

Prepare the batter by mixing all-purpose flour, cornstarch, rice flour, baking powder, and ice water. Heat oil to 350°F (175°C) and fry chicken until golden brown.

Drain fried chicken on a wire rack and toast brioche buns. Assemble with spicy mayo, chicken, pickled slaw, cilantro, and optional cucumbers.