In a dry frying pan, cook the cumin seeds for about 30 seconds until aromatic. Place in a pestle and mortar and coarsely grind. Combine in a large dish with the garlic, oregano, 3 tablespoons of the lime juice and the oil. Add the chicken thighs and coat well. Cover and refrigerate to marinate for at least 1 hour.
In a bowl combine the mayonnaise, remaining lime juice and vinegar then season with salt. Add the cabbage and radishes and toss then scatter over the coriander and lightly toss through.
Heat a barbecue to hot. Season the chicken thighs with salt and cook for about 5 minutes each side until cooked through. Place on a warm plate, cover with foil and rest for 5 minutes.
Just before serving, heat the tortillas quickly on the barbecue. Serve the tortillas with the chicken, coleslaw and hot sauce.