I've sent money to a couple of my GFs accounts & sending the money is just the same as when you 1st sent it to yourself, you just need their banking details. The Gift/Tax part is trickier, even more so as your're not married as technically the Gift needs to be for a specific occassion, I've sent money over to the GF for Birthdays & Xmas BUT I'm not 100% sure I wouldn't get hit for tax on this if I was audited - I did see something about "Having a moral obligation to Support" my GF which if you have children could be used but as we don't I've stuck to the "Occassion" gifts. Recommended method is she has an account overseas, you formally document the gift there and she sends it to her Thai bank account, but this is impossible for most people, it's hard enough for me to set a Bank account up in the UK never mind set one up for my GF.
