Does your Windows setup support Thai fonts?

Yes, it does.

Try to change your font in Windows Setting and QuickBooks to Tahoma or Arial Unicode. Any luck?

You can also install the trial version of QB Desktop 2021 to compare. 

Hello there, @cftikklji. I understand the importance of changing the language display in QuickBooks Desktop. Let me share some information about this.

All versions of QuickBooks Desktop (e.g. US, UK, Canada) exclusively support the display of the English language. With this, I will consider this as a suggestion to improve your experience with the program.

As always, you can visit our QuickBooks Community help website if you need tips and related articles in the future.

I appreciate your patience and understanding. If there's anything else you need, please let us know. The Intuit Community is always around whenever you need help.