Mix all Ingredients together in a bowl (except the chicken thighs). Once mixed well, add in the chicken and coat all the pieces well. Cover the bowl and refrigerate- or pour the contents into a Ziploc bag and refrigerate for at least 24 hours.
Take the chicken out and place into a colander to drain off the yoghurt marinade. You will want to remove as much of the marinade as possible by wiping it off.
Spray your grill grates with some oil. Turn on your barbecue grill and get it to a nice, hot temperature. Grill the chicken for about 7 minutes a side until they are cooked though.
Remove chicken, cover in foil, and let rest for 5 minutes before serving warm with naan bread.
Garnish with lemons, parsley, sumac and red pepper flakes.