I have a similar problem that also occured overnight, but with both ears, .. the high pitched ringing is Tinnitus which i have too, but i seem to have it under control now ...with constant Vestibular Exercises
i have seen Specialists in the UK & here at Bangkok Pattaya Hospital ENT Dept.. they have Two specialists that come from Bangkok one is an elderly lady Professor 70 + who comes twice a week, the other is a lady in her 40's who seems to come when she has time, both of them have confirmed my hearing days are over 95%,.. having had multiple hearing and balance tests which are not cheap of course.....I'm sure u will find a wider range of ENT doctors at Bumrungrad Hospital in Bangkok