a visa arranged in UK isn't a guarantee of entry.....they can still stop you from coming in if they want to. Get a new passport and/or marry your g/f. (y)
ignore it if you're working and here legally already. If you're retired though then it's worth considering. You don't get the 500k back though so it's 100k/year for a visa. Still not bad - if you've got the money.
doesn't your friends small business provide him with a visa? If so his company cannot provide you with one - unless he increases the capitalisation of his company. But then he will need to employ additional Thai staff.