I find many speakers from the southernish bit of Asia to be difficult to understand - Thai, I’ve noticed, as well as India. I think it has something to do with rhythm or something. I have no problem with most foreign accents.
I once had an interesting experience on jury duty. The defense attorney was Jamaican-American, with an accent. One of the witnesses was an Asian Indian doctor, with an accent.
When the doctor was questioned by the prosecutor, who had no discernible accent, (to my ears anyway; he sounded like a typical middle-American) I had no trouble understanding his testimony.
On the previous (and subsequent) days of the trial, whenever the defense attorney spoke, I had no trouble understanding him. In fact quite the contrary; I found his way of speaking clear and precise, and his accent very pleasant.
But when the defense attorney questioned the doctor, I had to concentrate intently to understand either of them. Something about the by-play between the different accents made things quite difficult.