Can I renew my non-B visa on its expiration date without issues?

Not advisable to do it on the last day as you may need more documents

Next year you should start your planning much earlier as in Bangkok you can apply for your extension when you have 45 days or less remaining on your current stamp

There's no real need to wait until the last day and there's no need to make an appt if you don't want to

You can apply for a new extension at most all offices when you have 30 days or less left on your current stamp. You don't lose any time applying early the new extension is added to your current expiration date

Most people don't wait until the last day because when you apply if you're missing a document, or something you don't have any time left on your current stamp and will run on overstay if you can't get it sorted out that day..

Still as long as you have your ducks in a row document wise, you should be fine, you're just cutting it really REALLY close 😮 Best of luck with it (y)