Ladakh Maxicab Union runs 11-seater nonstop Tempo minibuses to Manali with departures at either 8pm or 1am. Sign up a day or two ahead to get a decent seat. The journey can take anywhere from 15 to 21 hours.
The office is above a vegetable shop facing the J&K ATM as you enter the main bus station area. Don't confuse with the taxi cooperative.