Not sure about .m2ts files. But the .mkv container files seem to support a variety of foreign subtitles.
I’ve played movies that were spoken in Chinese, and had subtitles available in English, French, Italian, etc.
It will depend on the particular file and whether or not it comes with the subtitle data or not.
In other words, the subtitles themselves must be pre-generated and included with the video file. So you must check for subtitle availability on a per file basis.