I want to change visa exempt entry into Non-O in Bangkok but since I currently have ED visa, I need to go out of the country (I wonder why ED can not be change to Non-O but tourist visa or visa exempt can). Can I do a trip to Aranyaprathet, cross to Piopet, play at casino a little and return the same day to Thailand? Anyone has a recent experience?

You can contact the forum sponsor advertising to the right. They use a different border posts that is better than Poipet. If you insist on the the latter I recommend you get an e-visa for Cambodia, to save a passport page and void haggling with touts and corrupt officers.

I need to go to Aranypratet and I go with my car since it is just about 3 hours of drive. Cambodia visa is no problem but I need to know if I get 30 days going back (I am from a country that should get 30 days on land borders) on a visa exempt and if I can go back the same day.

I'm sure you have read this before, if from a G7 country you are allowed 30 days at land borders, and you can re-enter the same minute if you so wish.

You cannot change non immigrant visa classes. You can normally change the reason for an extension of stay but immigration has been flip/flopping on this so you never know now.

You can only change from visa exempt or tourist visa entry to a non immigrant visa entry because they are not non immigrant visas.

Since you are not currently on a visa exempt entry you should not have a problem getting one.

Driving a little further to Ban Laem would make you crossing quicker and easier than Poi Pet.

Thanks, Joe, much appreciated. I will consider Ban Laem, too.