Cook the bacon in a skillet over medium heat until crisp. Remove it to a plate, crumble it, and set it aside for topping.
Add the diced potatoes, sliced leeks, chicken broth, salt, black pepper, and thyme to the slow cooker. Stir to combine.
Cover and cook on low for 6 to 8 hours until the potatoes are very tender.
Stir in the heavy cream and shredded cheddar cheese until the cheese melts and the soup turns smooth and creamy.
Ladle the soup into bowls and top each serving with the crumbled bacon.