Install xiterm+thai by entering the following commands in the terminal:
sudo apt update sudo apt install xiterm+thai
Description:
X terminal program with Thai languague support
xiterm+thai is an X terminal emulator program with Thai language support. It has built-in Thai keyboard input support. You could also use the X11 XKB extension to input Thai characters. . A Thai TIS-620 font, such as one from xfonts-thai-nectec is needed to display Thai characters.
Homepage: http://linux.thai.net/projects/xiterm+thai/
Version: 1.10-2
Section: universe/x11