In a saucepan, submerge the chicken in cold water and simmer over medium heat for 10 minutes until cooked through. Let it sit for 15 minutes to cool, then shred the chicken.
In a large bowl, toss together wombok, mint, coriander, carrot, cucumber, shallot, and bean sprouts. In a small jug, whisk together chilli, lime juice, fish sauce, and sugar.
Combine chicken with salad, drizzle over dressing, then serve in bowls and sprinkle with peanuts.