Language display for recent document list

Apart from English, I sometimes need to type in Thai. That’s no problem in itself, but although I can save filenames in Thai, (I have checked that, it does it OK) the Recent Documents list in Writer displays the filename as a series of squares. It looks to me as though perhaps I need in add/install some Thai language settings?
I need to keep everything else in English - the menus, etc, but just want to make LO Writer display filenames in Thai as well as English.

I don’t have much experience with foreign languages symbols but I found this which might be useful to you:

Sorry that didn’t help, as I have East Asian Language support installed already. I’m guessing it must be something specific to LO that I need to add? Before LO5 it displayed the recent docs list in Thai OK.