What is the reason you'd want to come in free stamp?
So you're not wanting to apply for a yearly extension of stay based on marriage to a thai?
You leave without a re-entry permit, you lose the stamp you're on, meaning you have to start all over from scratch with first the 90 day Non-O, then the year extension after that
Nothing happens, they'll stamp you out without any issues.
but with that being said
if/when you come back, should you ever try to go for a long-term visa/extension they will see that you didn't follow the rules like you were supposed to and cancel your previous extension based on employment before you left and they will fine you.
That's because just stamping out of the country does not cancel an extension officially with the immigration office it just lets you leave.
Now on the rare chance you are on the initial 90 day entry from a non-immigrant type B Visa based on employment (as in, you have not ever extended it), you can just leave in that stamp will cancel when you go out
nope you're far from the first person who left the country on a valid extension/re-entry, went and got a DTV then came back in
Most don't bother cancelling their earlier extension
I'm just saying you COULD do that at the immigration office and they would know exactly what you were doing (jumping on the DTV band wagon 😛)
You are correct, even if for some reason you were stamped in on the old extension/re-entry you'd be fine as long as you left before it ran out. Then comin' back just show the DTV print out and you'd get in on it
IF you just received your 90 day single entry Non-O visa you won't be applying for ANY "marriage visa" once you get here 🙁
you'll get stamped in for 90 days on the current Non-O and then when you have 30 days or less you'll go apply for a year "extension of stay" based on marriage <- which is not a visa 😉
Be that as it may
you are unlikely to have issues flying in on a valid visa with a one way ticket. You won't have any problem with passport control when you stamp in showing the PDF print out along with your passport
BUT
You should check with your air carrier because they are the people that enforce onward travel rules. I would imagine because you have a valid 90 day single entry visa you would be okay comin' in one way, but check with them for sure
are you "required to" go cancel that extension no you're not, but you're going to have to watch stamping in each time on the DTV as long as the old extension re-entry are valid so you're not stamped back in on it
you can go out to the immigration office that issued your extension/re-entry permit and get them to cancel them.
I mean you're stamped in on the DTV now so that's fine, you're not on that extension anymore
It's far safer than trying to explain to them that you went to get a new visa while you still had a valid extension re-entry each time you stamp in until your old extension expires