Heat a large wok or frying pan over medium-high heat. Add the oil, chicken, salt and pepper. Stir-fry for 5 minutes until the chicken is no longer pink.
Add the garlic and ginger; stir-fry for 1 minute until the garlic is fragrant.
Add the soy, sugar, sambal and water; stir to combine. Cover the wok with a lid or a baking sheet. Reduce the heat to medium-low. Cook for 10 to 12 minutes, stirring occasionally, until the sauce is thickened and the chicken is cooked, adding a little more water if the sauce is too thick or the mixture seems a bit dry.
Add the red pepper and stir-fry for 1 to 2 minutes until the pepper is softened a little.
Add the cashews, green onion and basil. Stir-fry for 1 minute to combine. Serve the stir-fry over rice.