Dry-fry the chorizo in a large, heavy-based saucepan or flameproof casserole dish over a medium heat for about 2 minutes, stirring continuously. Add the oil and chicken and increase the heat slightly, then cook for about 5 minutes until coloured all over, stirring occasionally. Remove the chicken and chorizo from the pan using a slotted spoon and set aside.
Add the onion, celery, garlic and capsicums to the oil remaining in the pan. Cook, stirring frequently, for 5 minutes until the vegetables are softened slightly. Stir in the rice, tomatoes, bay leaves and thyme, then replace the chicken and chorizo and pour in the water. Bring back to the boil, stirring occasionally. Reduce the heat to low, cover and cook gently for 25 minutes.
Add the peas and corn, forking them lightly into the rice mixture. Re-cover and continue to simmer for a further 5 minutes until the rice is tender and all the liquid has been absorbed. Discard the bay leaves and thyme stalks and season to taste, then fork through the parsley and serve.