Cut kernels from ears of corn to equal 6 cups; scrape milk and remaining pulp from cobs using the dull side of a knife blade.
Heat oil in a large saucepan over medium flame; add onions, thyme, and 1/4 teaspoon salt. Reduce heat to medium low; cover. Cook 8 minutes or until onion is softened, stirring occasionally.
Add corn kernels and garlic; cover. Cook 4 minutes; add corn pulp, water and remaining 1/2 teaspoon salt. Increase heat to medium-high; bring to a boil.
Remove from heat; discard thyme.
Place half of corn mixture in a blender.
Remove center piece of blender lid (to allow steam to escape); secure blender lid on blender.
Place a clean towel over opening in blender lid (to avoid splatters). Blend until smooth. Strain corn mixture through a sieve into a large bowl; discard solids. Repeat procedure with remaining corn mixture. Chill at least 4 hours.
Combine remaining ingredients in a small bowl. Ladle 1 cup soup into each of 6 bowls, top with 2 tablespoons avocado mixture.