well - first transfer to Revolut and from there to UK bank. Kind of stupid isn't it - instead of transferring directly from Thai bank to UK bank. Revolut is very good - but not for this.
no you don't need a Thai bank account anymore for paying with QR since Kbank and for example Moreta Pay has made it possible for tourists to do just that
would probably not work since 500. 000 in this case are supposed to cover 2 persons and the requirement is 500.000 for 1 person - something could happen to both