Heat oil in a frying pan over medium heat, and brown chicken thighs on all sides.
Pour honey, soya sauce, tomato sauce or ketchup, garlic, ginger and reserved pineapple juice into a slow cooker and mix well.
Place thighs in the slow cooker and turn to coat with mixture.
Cover and cook for 4 hours on High. Stir in pineapple during the final 20 minutes of cooking.
Mix the cornflour and water together in a small bowl. Remove thighs from slow cooker. Stir the cornflour mixture into remaining sauce in the slow cooker until it thickens. Serve sauce over the chicken.