Language of system and language of invoice etc

I am brand new to Manager and wonder about the following (had a quick look around but could not find an answer). I would like to issue invoices in Thai but would like to maintain English as the language of Manager itself. I have changed the language of the Manager, but now everything is in Thai.

Is there any way of doing this?

One way to do this is to switch language to Thai only when printing invoice. Then it will be in Thai.

Another (more elegant way) is to simply use custom invoice template written in HTML which will have invoice terms translated in Thai while the rest of the program will remain in English at all times.

Thank you so much! Very useful. I may try the custom template. I had already figured out the first solution.

Thanks again
Andrew