Automatic Thai font of Template does not work

I created a template, namely Garuda12, using Thai font, Garuda with the size of 12.

Font immediately changes to aakar when I press a key to enter a Thai alphabet.


I have to change to Garuda manually afterwards.
What should be done more ?

And does this question concern ?

TestFontGaruda12.ods (229.8 KB)
LibreOffice 6.4.7.2
OS: Ubuntu 20.04.3 on Oracle VM VirtualBox

But it does not happen in:
LibreOffice 7.1.6.2
OS: Ubuntu 21.04 on Oracle VM VirtualBox




I thought the problem was resolved in later versions.