In order to write an email in Thai you need to make sure that your email client knows that your message is in Thai. It may be possible to identify your email as being Thai by selecting the coding from the menu:
This should add an appropriate MIME header to your email to identify the type. The client may also switch to a font suitable for viewing your message properly.
If it is not possible to tell your client your email is Thai then you need to
manually modify or add the Content-Type
header to the email. In some
email clients you can add this header:
Also see the section on Thai MIME headers.
At this time, none of the webmailers seem to support user selectable character codings. Using Yahoo I have successfully sent UTF-8 and HTML to other Yahoo accounts but when I sent it to Hotmail it was transcoded or the HTML was quoted. If you enter UTF-8 text, the mail webserver is prone to convert it to something else.
So how do we send email, confident that it will get through ? The only way is to write your message and attach it: this will avoid transcoding. It means the receiver must save the attachment and open it in an editor in order to view it. Writing a quoted reply is also awkward.