@Steve ********
Perhaps you had an issue with NatWest because they do not allow their customers to be residents of Thailand. The following is their permitted list of countries. They may have been concerned about flagging a regulatory issue.
Austria, Bahrain, Belgium, Bermuda, Canada, China (Expats only), Denmark, Finland, France, Hong Kong, Kuwait, Norway, Oman, Qatar, South Africa, Sweden, Switzerland, United Arab Emirates, United Kingdom or the United States of America