Lay the chicken thighs in a non metallic dish so they are in one layer as much as possible.
Squeeze over the lime juice and add the scallions, garlic, soy sauce, onion, thyme and tomatoes. Season well and mix everything together. Leave everything to marinate for 2 hours, or overnight if you can.
Take the chicken pieces out of the marinating mixture and pat dry with kitchen paper.
Heat the oil in a deep frying pan set over a moderate heat. Fry the chicken pieces, turning frequently, until the chicken is golden.
Spoon over the reserved marinating mixture, stir in the tomato ketchup, and add about 1/2 cup hot water – or enough to barely cover the chicken. Cover the pan and simmer for 20-25 minutes, until the sauce has thickened and the chicken is tender.
Serve with rice and peas, plain steamed rice or pasta.