A question regarding medication.

I'm type 1 diabetic and as such in the UK all my prescriptions are free.

How do you go about 'transfering' my prescription and what are the costs like?

I am after a bit of advice regarding a friend who is currently in quarantine hospital and now on an overstay. He entered the country on the 30 day visa exempt and was due to fly out on the last of his 30 days but tested positive to covid on the fit to fly test. He was then sent to a quarantine hotel/ hospital in Bangkok but then due to running out of meds for diabetes was sent to a hospital to finish off his quarantine period. He is aware he's heading for a big overstay but I'm here seeking any advice or options he has to avoid the dreaded stamp in his passport or even reduce the cost when exiting the country?