I had to use that last year on my initial 90 day entry to Thailand as we weren't in Chiang Mai for the house visit in October, that's why it pushed my visa expiration date back to the end of November. Not sure if that exempts me from doing it now?
yeah I was thinking that this may be my only option but worried as I have a couple of weeks from when my visa expires until I leave the country in December and I don't want to overstay so I might have to leave the country before then and come back as a tourist. Then apply back in the UK over Xmas?