How does traveling outside Thailand affect the renewal of a NON-O Marriage Visa and re-entry?

Your problem isn't applying early, 45 days before it expires. Your problem is the 30 day under consideration stamp from the time you apply. At the earliest that would put you having to return on June 30th, as it is 45 days from the expiry date. It is no different starting over as it is doing your yearly renewal. You've already got all your documents, or you should have, and just like your renewal, all you need is new bank letters, and new pictures. Everything else is the same, as long as you still live in the same place. The only document you might need to go to the Amphur and get new copies of is your marriage license and registration because the first time immigration wants the original, and starting over would be just like the first time. On yearly renewals they just need a copy, but they want the original the first time. That is the only problem I can see. Immigration has a tendency to consider your visa extension as the most important thing in your life, so don't count on them making an exception. If you are using Chaeng Wattana they had an officer rotation in section L last year, so they are being sticklers for the rules, and not giving any leaway. For your re-entry, if you can't get it renewed before you leave, if you take copies of your marriage license and registration, and copies of your wife's ID card, and the house book she is listed in, then you can apply for, and get a 90 day type O visa to come back on instead of a tourist visa. This can save some hassles. Just a two day delay on when you leave would make a world of difference. Then you could renewand just get a re-entry permit to come back on.

You can renew 45 day prior , i guess.

Some offices allow 45 days prior for renewal. If your extension expires when you are out of the country then you’d have to start the process again from scratch.

Your immigration office may allow you to renew slightly earlier if you can show them why you need to do so. Not guaranteed.