Spoken and written Thai are not correct.

I was looking the movie " The Oxford year". in Thai with thai subtitles. I soon found out, that the spoken Thai and the thai subtitles doesn’t match up. Only sometimes it was correct. Can I do something to change this?

It’s very common with Thai stuff. The sound is colloquial speech whereas the written subtitles are more formal. You can try using the ASR, or sometimes there are multiple subtitle tracks on a single video - one of them may have a closer match to what is actually being said.