If you have been outside the UK for less than 91 days in each and every tax year yoou may be able to claim tax back as a non resident. If you did not when you left the UK you should complete a Form P85 and send it to your tax office. On receipt HMRC will make you non resident for the tax year after your departure and furthermore split th leaving year into two portions, one resident and one non non resident. The form is available on the web and can be filed on line.
HMRC will then tell your employers not to deduct tax, merely NI which you need to keep your card stamped to use an old expression.
By the by I have a Thai wife!