Up at 06:00 to get the bus South. A transfer to another bus in Siem Reap followed, about 5 hours later, by a transfer to another bus in Phnom Penh. God knows how many hours later get to the border and check out of Cambodia into Vietnam. Arrive near the hotel in District 1 at almost 22:00.
My advice? get a flight at about £100 and save yourself a day of abject boredom and torture. The luxury bus wasn’t, it was uncomfortable the whole way.
Check into the hotel, get something to eat and go to bed….