Small report: Just passed through Nong Khai Immigration (approx 19.00, taking the Vientiane - Nong Khai bus). I've lived in Thailand before, but this was my first visa-exempt border bounce. I spent 1 week in Luang Prabang before coming back. Upon arriving at the checkpoint, the first policeman sent me to Room 15 to speak to the supervisor. He asked me what I was planning to do and to see my ticket out (which I had thankfully bought in advance), but did not ask to see ฿20,000 or any confirmed hotel bookings. I hope this helps someone.