1.Dry the chicken with a paper towel. Using a sharp knife poke holes on all sides of the chicken.
2.In a large bowl combine coconut milk, tom yum paste, coconut oil, fish sauce, lime juice, brown sugar, garlic and lemongrass. Stir mixture to combine.
3.Add chicken to bowl and then gently massage the chicken to thoroughly coat it in the marinade. Allow the chicken to marinate in the fridge for at least one hour; up to overnight.
4.Take the chicken out of the fridge for 20 minutes prior to cooking. Position the top rack of the oven about 3 - 4 inches from the heating element. Set the oven to high broil and let it preheat.
5.Place the chicken on a sheet pan covered with foil in a single layer. Pour all of the remaining marinade over the chicken. Broil chicken for 3-4 minutes then flip to the next side and broil for 3-4 minutes or until the chicken is fully cooked.
5.Allow the chicken to rest for about 10 minutes before transferring to serving dish. Garnish with chopped cilantro just before serving.