Yes, this is the way if you prefer to do it this way. And you dumped the Non O by leaving without a re-entry permit an applied i Aus or outside Thailand.
I guess you mean the initial 90 days Non O visa based on being married to a Thai? You can apply for a re-entry permit for the 90 days at your immigration or the airport at 1000 baht. If that’s your point.
Regarding the one year extension of stay the requirements varies a bit between the different immigrations so I suggest you’ll get handed over the requirements at your particular immigration before you apply. Regarding financial requirements the 400K baht has to be seasoned for two months before you apply unless you apply with an affidavit letter from your embassy regarding income. You can apply for multiple re-entry permits on the one year extension of stay on a TM.8 form at 3800 baht.
Yes the downside with Non O is that you’ll need to seasoning some of your own money in a Thai bank (800K baht) unless your embassy provides you an affidavit letter regarding income. But it’s still your own money in the end of the day. Privilege you just pay for and none of benefits are defendable unless your not passed 50 years.