Very,very nice, excellent shape. I think that niveum var ang-thong is now know as Paph Greyi. RHS have Paph Ang-thong and Paph Greyi listed with the same parents... P.godefroyae x niveum.
I think it is/was known as a Natural Hybrid, not a species.
The clone you have is one of the best I have seen.
There is no such thing as P niveum var. ang-thong, and to my knowledge never has been. Chien is correct, ang-thong is a variety of Paph godefroyae, not of niveum. These markings are far too delicate for P godefroyae. I believe this is a straight niveum. It is a very beautiful flower.