Wipe the chicken breast fillets with paper towels. Cut into one-inch cubes. Place in a bowl. Add half a teaspoon of salt, a quarter teaspoon of pepper and a quarter teaspoon of cayenne powder. Mix well. Set aside.
Make the batter. To the rice flour and water mixture, add half a teaspoon of salt, a quarter teaspoon of pepper and a quarter teaspoon of cayenne powder.
Add the batter to the chicken. Mix well. Add the starch. Mix well again. There shouldn't be any loose batter at the bottom of the bowl.
In a wok or frying pan, heat enough cooking oil to reach a depth of at least two inches. Heat until fine wisps of smoke float on the surface.
Drop the battered chicken into the hot oil, one piece at a time to make sure that they stay separate from each other. Cook for about two minutes or until golden brown. Depending on how large your wok or frying pan is, you may have to do this step in batches.
Scoop out the chicken cubes and drain on a rack or a stack of paper towels.
Pour off the oil from the wok or frying pan leaving only about a tablespoonful.
Reheat the oil. Saute the garlic, ginger and chilies for about a minute. Throw in the bell peppers. Stir fry for half a minute. Add the pineapple chunks and cook for another half a minute.
Add the cooked chicken to the pan. Pour in the sweet chili sauce. Toss to coat every piece of chicken, bell pepper and pineapple with the sauce.
Serve the sweet chili pineapple chicken at once. We like it with rice.