First question is - in which country are your assets ?
Make your will in UK if your assets are in UK
Make your will in Thailand if your assets are in Thailand
If your assets are in both countries than make separate wills in both countries.
There are many English speaking solicitors in Thailand who will make a will for you.
"I would like to do another one in Thailand to cancel the one in the UK out".
I would take further advice on this- I don't know if a will in Thailand will be legal in UK.
found on google - you need a Will to be drawn up for each jurisdiction in which you hold assets, and the document must be written in the language of those courts. You cannot submit a Thai Will to the courts in the UK, and likewise, and UK Last Will and Testament would not be admissible to courts in Thailand.