Saute rice with butter until golden brown. Slowly stir in chicken, salsa, water and seasoning packet contents. Stir in corn; cover and simmer 5 to 10 minutes or until rice is tender and chicken is no longer pink inside.
To serve, arrange lettuce on each plate. Top with chicken mixture. Sprinkle with cheese, tortilla chips and tomato. Top with guacamole or sour cream, if desired.