Paph Thaianum (leaf or bud?)
 

I have a paph thaianum but I do not know when is its blooming season. So I am wondering if this is a bud or a leaf.

It could be a bud, and you can probably tell by gently pinching the plant at the point where the leaf is emerging - if there's a bud there you'll be able to fell it. If not, the center of the plant will feel flat.