How do you request to come back to your previous unit after a Korea tour?

You can try branch...but don't hold your breath

You probably won't come back to your same unit. When you are filling out your levy packet, you will get offered a HAAP assignment. Sometimes it is to return to the same post. If you don't get that, then you will just have to try to reenlist for it when you're in Korea.

Pretty sure that it requires the sacrifice of your first born, three pinches of fairy dust, an auspicious star alignment, and reciting a mantra three times while looking into a mirror in the dark at midnight.

But I could be wrong.