I believe Nha Trang region in Vietnam (where Amanoi is situated) receives most of its rainfall during September - December, so might be a bit wet to visit Amanoi at that time.
North Vietnam such as Hanoi/Sapa sees better weather, November is also a good time for Luang Prabang in Laos (I read that you were asking about Amantaka in the other post).
Lush landscape after rainy season and high water level along the Mekong river with clear skies.