In a large pot, cook the chopped bacon over medium heat until crispy. Remove the bacon and set aside, leaving the drippings in the pot.
Add the diced onion and celery to the pot and sauté until softened, about 5 minutes.
Stir in the diced potato, reserved clam juice, and enough water to cover the potatoes. Bring to a boil, then reduce heat and simmer until the potatoes are tender, about 15 minutes.
In a small bowl, whisk together the flour, milk, and cream until smooth. Gradually add this mixture to the pot, stirring constantly.
Add the cooked bacon, clams, thyme, salt, and pepper. Simmer for an additional 5-10 minutes until heated through.
Taste and adjust seasoning if necessary. Serve hot, garnished with chopped parsley.