You could try to ask them to reissue your ticket based on the current fares (which hopefully have not moved much) while keeping the same flights and booking class. Thanks to THB and EUR tax, there would be most likely a little change in fees meaning you would pay something small (or get a partial tax refund) and get a ticket with an issue date at a time when the new allowance is enforced. "slightly" circumvoluted approach, but why not