Mix together chicken broth, oyster sauce, soy sauce, fish sauce, sugar, brown sugar, and ginger in a bowl.
In a large pan, heat the canola oil over medium-high heat. Add the coarsely chopped chicken thighs and cook until no longer pink. Add onions, garlic, red pepper, and chilies, and cook until juices begin to caramelize.
Pour in the prepared sauce mixture and let it cook until it thickens and caramelizes slightly.
Stir in the fresh basil leaves and cook just until they wilt. Mix in chopped cashews.
Serve the Spicy Thai Basil Chicken over rice and garnish with additional basil leaves if desired.