! year visa question

Yes, you need to get a visa on arrival for Cambodia. Not sure about the current cost but you usually have the option of doing it yourself or paying someone to do it while you wait around. You need a photo.

In my experience you can leave the Cambodian immigration building, turn left, get an exit stamp at the booth and then walk back to the VN side, but my situation was different from yours, as I was getting a new visa both times.

Here is a thread that discusses your situation of crossing and returning on a one-year tourist visa:
https://www.expat.com/forum/viewtopic.php?id=824846

jeflaq wrote:

I'm currently living in My An, Dong Thap province. I need to leave the country one time to satisfy my visa requirements. I'm from the USA here on a 1 year tourist visa. I've heard, I can get a bus to Cambodia From Cao Lahn. My questions are: Do I need a visa to enter Cambodia? and can I cross the border and turn around and come back? Thanks for your help.

You're right. You need to exit and re-enter to legalize your visa. Cheers!