its the same process as when you extend for 30 days. You submit another application and then pay 1,900 Baht and they will see that you already have an extension, and deny you 30 days but then give you 7 more days.
You can only apply for the 30 days extension once per Visa. Since you would have already extended until January you have to leave by that date (which you said you cant because your flight is 2 days later) so you need to apply for the additional 7 days after the 30 day extension, which will cost you 1,900 Baht
You can go back to Immigration and pay 1,900 Baht and they will give you an additional 7 more days. I would do this than risk overstaying and getting that marked on your record
Mike Verest the extension just gives you an additional 30 days. So when that time is up you travel out somewhere and then you can apply for a Tourist Visa again and then come back and extend that for 90 days. Or if you don't plan on staying in Thailand longer than 30-60 days you can just re-enter on a free 30 day visa exemption.
People have been getting extensions on 30 day visa exemptions and then back to back Tourist Visa in Laos and other bordering countries for years. This is your first time doing it, you shouldn't need to worry about anything...
why not just book a round trip ticket out and back in for 2000 baht or less and then you get 30 more days. seems like a waste to spend another day at immigration and spend 1900 for a measly 7 days.
You only report to immigration if you want to stay longer than your Visa. In your case, 60 day Tourist Visa, you will report to Immigration for them to extend it to 90 days total. If you don't want 90 days, then just depart before the date on your visa.
There are no rules that limits you to how many times you can fly in/out, so you should take advantage of the free 30 day visa exemption especially if you aren't staying longer than 30 days this time, there's no reason to apply for a Visa. But next time it is more convenient to stay 60 days with a Tourist visa plus 30 day extension (90 days total) so you don't have to fly out/in after only 60 days.
I would forget about the re-entry permit. Use that money to get a brand new Tourist visa valid for 60 days before you come back. Or just forget about the Tourist Visa and use the free 30 day visa exempt and then pay 1900฿ to extend it to 60 days.