Comparison of Popular Thai Fonts
Although all computers have the ability to display Thai writing, they may not necessarily have the fonts installed that you want. Individual programs also may not display Thai writing correctly. Catherine Wentworth has produced a PDF document to demonstrate a number of the fonts that are freely available on the web to download and install.
Garuda is a popular and very clear font
Krungthep A very clean modern font.
Purisa is this the Comic Sana of Thai fonts?
Thonburi another very popular font
You can download these and many other Thai fonts from the following sites
How to Install Fonts on Your Computer
Thai Script Typographical Styles: