worrab

Yet when I flew back in July this year with BA, both trips were fully booked. Not a spare seat anywhere!!

Now I understand.

So the OP is okay to go south to do his first extension of stay then and not have to go to CW?

Back on 21st Sept 2015, I arrived on a tourist visa. Then on 23 Sept this was converted to a 90 day Non-O Retirement in CW Bangkok. On 16th Dec, I then applied for my first Extension of Stay based on Retirement in Prachuap Khiri Khan. So the OP can move south before completing his first Extension of Stay.