I'm flying to Thailand on Thursday morning on a METV with a return flight to the UK on 30th April 22. My original plan was to go and see my elderly sister in Perth WA for a week or so during this time and then return to Thailand. If things don't open up and I can't do the WA run then do I have an option to change my METV in order to stay in Thailand for the duration? Thanks for any advice.