Yesterday I did a Poipet visa run. Things have changed. I had an e-visa to Cambodia, leaving Thailand and entering Cambodia at Poipet with no hassle at all, queues maybe 20 minutes in the middle of the day. Only thing had to fill in an arrival form. Every passing of an immigration counter (Arrival and Departure) on both sides (Thailand and Cambodia) involves full fingerprint scanning of both hands and thumbs.
Came back this morning through Poipet departure immigration again 20-minute queue, counters were well-staffed. Check check, stamp stamp, and go.
To my dismay and worry, at the Thai arrival immigration, there are no longer any counters for filling in visa-on-arrival forms, or maybe there never were, this is the first time I went to Poipet. I asked a staffer and he said "No need", which made me more worried. I joined the 20-minute queue hoping for the best. Again, well-staffed counters. At the counter, the officer studied my passport and said (politely) "|You have no visa to Thailand, what is the purpose of your visit?". I explained honestly and in detail what my purpose was in Thai and she stamped me through without having to pay a single Baht for on-arrival-visa. I think because the purpose of my visit was not 100% tourist related but very justified, I was stamped through, but don't do this on a previous tourist visa. What I mean is, don't go to Poipet for regular tourist visa runs, it will not work unless you are using some agent.