Update on Poipet Cambodia/ Arunya Prathet Thailand border crossing.
I got a visa on arrival for B2000 (take spare passport photo) but it is highly recommended that you stay one night.
Otherwise the Thai officials could reject your re-entry and you have to start all over again.
Get the exit stamp from Cambodia officials the next day for B600
Walk across the Friendship Bridge to the Thai Immigration to re-Enter, pick up Departure Card and fill it out.
You need to go up one level; try to take the stairs on the right hand side not the escalator on the left; you will save yourself an hour or more of waiting.