The issue you posted was not related to the IVS.
I have seen your screencast, but it was hard for me to reproduce the issue.
Can you explain which key you have to press to reproduce this issue using the Thai keyboard, or may be EmEditor’s Insert Special Character command. I am using English keyboards, and I don’t know which key sequence do I have to press in Thai keyboard, or which Unicode characters I have to enter.
Thanks for your patience.