There are several companies offering remittance services from overseas with rates that are better than your bank and with lower fees. Moneycorp.co.uk for example have a tie-in with the Telegraph offering this service.

Anyone on this forum have an account with these companies or use their services regularly enough to give a meaningful comparison?

Normally you get the best rate by sending currency here and letting the Thai bank do the exchange.

Probably because the Thai Baht is not something that overseas banks want or need to hold, with the possible exception of overseas branches of Thai banks, which are not numerous. There are comments about the Bangkok Bank transfer service here, which offers two options.

So the only advantage you may get from using a money transfer service is if you make a saving on the actual transfer fee, which varies from about GBP9.50 to about GBP40 for UK banks.

Obviously YMMV and you need to check the various fees/rates very carefully in order to arrive at a decision.

Personally I just get my bank to send currency via SWIFT at a cost of GBP20, not least because I only need to email them to get them to do it.