On a cutting board, season the chicken thighs on both sides with salt and 2 teaspoons of the Fiery spice blend.
Heat the oil in a large skillet over medium-high heat. Once the oil begins to shimmer, add the chicken thighs and cook for 2-3 minutes, until golden brown. Flip and cook on the other side for 2-3 minutes more, until the chicken is cooked through. Transfer to a cutting board to rest for 10 minutes, then cut into cubes.
In a large bowl, add the fish sauce, warm water, lime juice, brown sugar, and the remaining 2 teaspoons of the Fiery spice blend. Whisk to combine.
Toss the cooked vermicelli noodles in the sauce until fully coated.
Divide the noodles between serving bowls and top with the chicken, cucumber, cilantro, mint, red onion, peanuts, and lime wedges.