The thaifilter(1) program is a filter that converts Thai text into three levels:
Base level characters (including any ASCII characters)
This system is called 3-Level Classification. The two main uses for files converted to 3-Level Classification are:
To direct printers to print Thai characters at the correct display level.
To view Thai text files on terminals that normally do not allow the multi-level (normal) display of Thai text.
Some newer printers come with 3-Level Classification software already installed. For that reason the thaifilter(1) program has the -x option that turns 3-Level Classification off.
The thaifilter(1) man page is supplied in the TLE 2.6 software, and is also available in printed form in Appendix D, "Manual Pages", of the Thai Language Supplement for Solaris 2.6: Release Overview.