1. In "For the Encoding:" drop-down menu choose "Latin1" and click "Choose Font..." button in Use the Fixed Font:, select "FixedDB ThaiText New"

(Caution   Any bullet (·) will be displayed as (·) as the picture below)

click picture to see larger image

2. In menu "Options" select "Document Encoding" and select "Western(Latin1)"

3. In "Netscape Mail" you will see some text small but you can read Thai Message and can write too