There are advantages of going back to UK for an AO visa, you use finances in the UK, and don't have to bank money in Thailand, and you can 2 years from it.
Ron is correct. You cannot apply for OA or OX visas in Thailand. HOWEVER, he should have added you can apply for an O visa in Thailand, from which you can get a 12 month extension, based on being over 50, provided you meet the financial requirements. You can apply for an SETV or METV in Hk, and convert it here. Sorry, don't ask my the fine points of how to, I use an agent.
Transferwise also issue a statement of your transfers, no-one yet knows what will or will not be accepted, but I am pretty sure between my bangkok bank statement and the transferwise statement I should have my bases covered.