Cut the chicken thighs into bite-sized pieces and season them with salt, pepper, thyme, paprika, and cayenne pepper (if using).
In a large skillet or saucepan, heat the vegetable oil over medium heat. Add the diced onion and bell pepper, sautéing for about 5 minutes until softened. Stir in the minced garlic and cook for an additional minute until fragrant.
Add the seasoned chicken to the skillet and cook until browned on all sides, about 5-7 minutes.
Stir in the rice, ensuring it's well-coated with the oil and mixed with the vegetables and chicken.
Pour in the chicken broth and add the drained diced tomatoes. Bring the mixture to a boil.
Once boiling, reduce the heat to low, cover the skillet with a lid, and simmer for 25 minutes until the rice is cooked and has absorbed the liquid.
Remove from heat and let it sit, covered, for 5 minutes. Fluff the rice with a fork before serving.
Garnish with fresh cilantro or parsley if desired, and serve hot.