That will depend totally on what she is watching.
If the video file has Thai sub-titles already included, the remote control button (number 7) "SUBTITLE" switches between sub-titles when playing.
If you want to try and find subtitles to download and play at the same time (or mux into an existing video), you would need to find an appropriate sub-title source website like:
https://subscene.com/browse
There may be more specific sub-title sites catering for the Thai language if you look around the web.
Topic: Thai subtitles (Read 2652 times)
