Put the onions, carrots, and celery in the olive oil in a large saute pan. Cook over low heat until they become limp. Add the stock, potatoes, thyme, bay leaf, and salt and bring to a boil. Reduce heat and simmer, covered, for 30 minutes.
Add the chicken. Cook for 15 more minutes and add the corn. Continue to cook for 5 more minutes.
For a delicious variation add a handful of chopped mint leaves just before removing the soup from the fire.
Put 2 tablespoons of rice into each of 6 soup bowls. Ladle 1 1/2 cups of soup into each bowl along with 1/2 ear of corn. Garnish with 2 tablespoons of salsa and 1 tablespoon of avocado.