If you apply non-o based on marriage visa before you go Thailand then no problem with airlines but if you come on tourist visa or visa extempt then expect you need return flight or onward ticket depends on your airline.
If you have Thai passport, why do you want to apply visa? When you leave your current country use that passport when you enter Thailand show your Thai passport π
Go to minstry of foreign affairs in laksi Bangkok if you take regular speed it's about 400 baht for translate another 400 for the stamp if you choose express it's about 1000. Don't forget to book an appointment before you go