I have a multiple entry non-Imm O visa and it expires in July. To renew it for another year do I need to reapply in the UK (where I am from) or can I do it in Thailand? 

I saw an ad on Deloitte Thailand's website that they are looking for an Assistant Auditor which I fancy, but I am reluctant to apply because I am not sure whether I need to have an existing working visa first before applying.

I know the salary in Thailand is far less compared to Australia, but I see this as an opportunity to experience working somewhere out of my comfort zone. I am not sure though whether the salary I will be earning is enough to pay for living expenses in Thailand (assuming I get the job).