How can I obtain a 90-day Non-O visa while in the UK to move back to Thailand?

Hi there..

I lived and worked in Bkk for many years, working at The Nation..blah blah...came back to the UK to take care of aged mum for seven years.

Now I want to move back to Thailand (Hua Hin) and researching the best way to obtain a 90 day Non O visa while here in the UK...i have read so much conflicting advice about the process, so if anyone in the know can shed some real light on this i would be eternally grateful. Cheers.