yes with imagration, but it's up to your airline if you have not got a return flight, within you alocated visa term,I get non o visa based on marriage,
You know with extension leaving Thailand and returning obtaining another visa elsewhere or doing the 12 months extension, you can't prove to the airline when you coming back, all I was saying is for a tenner a onward ticket, solves the problem and hassle if you get it,
but the airline is required to fly you back to you country of departure, if imagration refused you entry based on not having proof of leaving Thailand within you permitted stay.
iv been here 14 mate but when I travel back to uk for a couple of months as I will be next month, when I come back even with a visa I always but a cheap £10 disposable onward flight.
Iv been asked twice in the last few years ,emirate airlines. for a tenner not worth the hassle.
do some research, if you don't have a onward ticket leaving Thailand in the time permitted, whether it be visa exempt, or visa. You could be stopped boarding by your airline, so if you don't have a return ticket, a simple onward disposable cheap ticket will do,some people get asked some don't depend on your airline.