Is it OK to ask for a repetition?
Yes, not only it is okay but also it is necessary. You are the presenter. You are responsible for answering the questions from the audience. If you don't understand the question, how do you answer it?
What is the proper way to behave for the non-native speaking presenter?
This depends on the situation. In my personal experience (I am a non-native English speaker), I would first say
I beg your pardon, would you please repeat your question? (An old fashion way).
After the asker repeats the question, if I still don't quite understand the question but I have some clues about what the question is (after all, the audience are in the same or close fields), I would say
It seems that you are asking blah blah ..., is my interpretation correct?.
If the asker agrees, then I answer the question if I can.
If the asker disagrees, if I am lucky, hopefully he would rephrase the question or some audience would volunteer to help to explain the question. If I get it, I would answer it. If I still don't get it, I would say
Can we talk about this offline?.
After the presentation, I would go to the asker and ask him to clarify the question and then answer the question if I can.
The above probably won't solve all the cases if you are not lucky. One of my worst personal experience is that an asker who is also a non-native English speaker asked a question that nobody in the room including myself could understand what he was talking about after several repetitions. I had to give up and I could not find him after the presentation.