you have to do it where your TM30 is registered. So if you're on Koh Lipe in a hotel then they should do a TM30 for you, as required by law, then you can extend there if there's an immigration office there anyway.
You also don't have to do it on the last day. If you have less than 30 days left on your stay then you can do it now and the days will be added on to your current expiry date.
I tend to find Google helps with these kind of questions. Why? So you can look for things based on your interests, budget, etc etc, none of which you've provided.
it appears to be linked to the emergency decree being extended. I'd imagine once that stops being extended then the unable to travel crap will also go.
As an update, went along to Counter M armed with completed form, picture of myself, copy of TM30, copies of passport and any stamps/stickers associated with Thailand, plus print out of flight ticket out of here.
As expected the extension was rejected at counter M. No issues with this as I was given an extra 7 days to leave which is more than enough as my flight leaves over the weekend. The whole point was to avoid the overstay stamp at Swampy as I don't want any future plans to potentially be screwed up by that.
There weren't many people around the counter M area but there were around counter L, which I'm going to guess is area for the unable to travel due to covid malarkey.