In a large pot, cook bacon over medium-low, stirring occasionally, until crisp, 8 to 10 minutes. Using a slotted spoon, transfer to a paper-towel-lined plate. Increase heat to medium. Cook onion, stirring, until it begins to soften, 6 to 8 minutes.
Add flour; cook, stirring constantly, 30 seconds. Add broth and potato; bring to a boil. Reduce to a simmer; cook until potato is tender, about 10 minutes. Add broccoli, corn, thyme, and milk. Cook until broccoli is crisp-tender, 8 to 10 minutes. Season with salt and pepper. Serve topped with bacon.