Thanks for all the info gents,
I'm not the brightest spark when it comes to the internet, by process of elimination thought to check to see if any other forumites had the problem first. I have a hotmail address and I am the only user, this is the first time it has happened to me, where I cannot identify the sender.
Although the text is in Thai the mail address is in English ie: (Bigarch
noreply@example.com). It is not a big problem at the moment as it's only one or two a day. As Grasshopper says, I've been clean for a year or two and I have only just started to recieve them.