Yes, at least 4, 3 of them are deceased by now.
Two of them I only saw: Lungphu Ghia, Lungphu Laa, One I lived and trained under him for 15 years and only recently passed away, on jan 30th 2011, that is Luangta Maha Bua. One of them who is still alive, and I sometimes have the chance to talk to: Lungphu Lee.
You can say, whatever people want to believe that is the truth for them. They are all normal human beings, no special air, e.g. no conceit around them. You could literally walk through them, without them rejecting it, that is to say they have no conceit, that makes them protect themselves.
The only time it might be necessary to know if one is an Arahant, is then when one is stuck in ones practice. They will instantly know at what level of practice you are, and then be able to guide you in the right direction.
If you believe your teacher is an arahant, then trust in him, subdue to him completely and follow his teaching until you attain to what he has attained, then you will know if he is an arahant. Just remember what the Lord Buddha said: To fight alone an army of soldiers is easier than to fight oneSELF!. If you cannot trust or subdue, submit to a teacher, how can you get rid of SELF?
Even if in our ages a Lord Buddha would appear, we would not know and we would not believe, because our fetter of doubt is too strong. We so easily believe what science teaches us, not noticing, that science over the years of time is contradicting itself, telling us that they found new evidence that the assumption they made us believe in the past is not true. And now we have to believe the new assumption, that will be proven to be invalid as well in the near future.