Is the font installed but in your drawings?
If you are collaborating with users who do not use AutoCAD, they may need a corresponding TrueType Font (.ttf) version of the Tai script to view the text in Windows applications or web browsers. Plotting to PDF tai font 3t-unicode.shx
Navigate to your AutoCAD installation directory (usually C:\Program Files\Autodesk\AutoCAD 20XX\Fonts ). Is the font installed but in your drawings