Graham Lynch correct, there is some confusion here, but you are the one confused. Multi entry visa, valid for 5 years, 180 days per entry. You can exit and enter Thailand every 180 days and get a new fresh 180 days for 5 years, as many times as you like.
it’s definitely faster and cheaper to do an extension than leave for a day - but to each their own - there are plenty of cool places to go if you have the funds
I was asked for this and as an independent contractor I couldn’t provide these - they asked for my previous years tax returns and I explained my position in a word document and I was approved. Best of luck to you. (I also scheduled a dentist appointment and showed a copy of that, but I’m not sure if that influenced the decision)
If you have entered by plane you shouldn’t have an issue. If your crossings were by land already, fly out and fly back in. You may have reached the 12 month period for entering by land - but I am not sure how they track that.