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.
TLDR : Answer Summary
When crossing the Poipet Cambodia to Arunya Prathet Thailand border, visitors can obtain a visa on arrival for B2000, though it is advisable to stay one night to avoid potential re-entry issues. After leaving Cambodia, ensure you get an exit stamp for B600 before walking across the Friendship Bridge to Thai Immigration, where you will need to fill out a Departure Card. It is recommended to take the stairs on the right side instead of the escalator to minimize waiting time.