In a large pot sauté your onions, once they are soft add frozen corn. Cook until corn is a bit soft. Add your cans of creamed corn and rotel tomatoes. Add your cans of creamed potato, fill each can with milk and add to pot. Add your crab meat and seasonings (to taste). Stir to combine. Bring to a gentle boil then turn on low and cover. Allow chowder to simmer on low for at least 30-45 min so flavors can marry, stirring occasionally. Serve with a sweet cornbread or crackers.