Visas via london and e visa portals supposedly one of the most efficient so you shouldnt presume that and why wouldnt Thai passport renewal be in Thai its for Thai citizens
oh if IO in your district is ok thats good you can do all that, depends how many times you coming in and out whether to get multiple entry or single entry. Forgot costs i just get the multiple its 4000 baht
Better get the Non O wherever you are now this is 90 day visa. Then you apply for a years extension.
Do you already have bank account as funds will be needed in Thai bank account for the extension (not the initial 90 day visa) and dont think you will be opening bank account with a visa exempt stamp