Just done it myself online this year...quite easy. Went to BKK and wife got her biometrics done after booking online. She got her visa approved a couple of weeks after that.
I work overseas and have not been able to extend my Non O based on Marriage 3 times in the past and losing again this month. While traveling in and out on a Tourist Visa I was only asked once why don't I get or extend my visa... simply because I am not here long enough to process it. The immigration guy was ok with answer and actually the guy beside him said our system is not easy for you guys trying to do the right thing. There was a crackdown just before that I know several people turned away...but that was quite a few years ago.