Cook rice according to packet directions. While rice is cooking, heat a wok or large frying pan over medium-high heat. Pour in sesame oil and stir in onion. Fry until golden, then add garlic. When garlic is lightly browned, mix in prawns, ham and chicken. Fry until prawns are pink.
Lower heat to medium and stir in celery, carrot, green capsicum and peas. Fry until vegetables are crisp-tender. Stir in beaten egg and cook just until egg is scrambled and firm.
When rice is done, mix thoroughly with vegetables and stir in soy sauce. Adjust seasoning to your preference and serve immediately.