We are leaving Thailand after a long stay on a non ED student visa(and a few tourist visas before). No overstay.

 

One week later we have to fly to Europe from Vietnam with a stop in Bangkok.

 

Obviously we both now get rejected entry if apply for the usual free 30 days, especially one week after finishing the non ED and coming back.

 

How transit in BKK works? Can we stay on the airport for a few hours without passing immigration? We just need to wait for next flight.

 

 

Thanks.

I doubt very much you would be denied a 30 day visa exempt entry. If questioned show them you have a connecting flight out of the country.

You can only transit through the airport if your connecting flights are arranged in advance. In many cases they must be on the same airline.

Thanks , how you doubt it ? ???? after reading here what’s going on with them lately, how wildly they deny people with proper visas based on some “first impression”, no rules, do you think it would look ok to them that 2 young people just left their country after almost a year are coming back again after a week ? 

You'd have proof of your onward flight, that should make it clear enough that you're just passing through. If possible, book both legs on a single ticket, there's a good chance that you won't need to go through immigration at all - check with the airline(s).

If really concerned (and I do not think you need to be) bear in mind that you have the option of getting Thai transit visas.