Vietnamese people usually simplify names of some countries when they're talking. E.g: Nhật Bản -> Nhật (Japan), Hàn Quốc -> Hàn (Korea), Ấn Độ -> Ấn (India), Thái Lan -> Thái (Thailand), etc.
Remember that we just simplify names of some countries. ;) And unfortunately, Hà Lan isn't included in those some countries.
I believe Hà Lan - Holland is only the informal name of the Netherlands. Because of this misconception, we never have a translation for "Netherlands". (or at least that I know of).
It's complicated! :D I live in the Netherlands. The Kingdom of the Netherlands consists of FOUR independent countries: the Netherlands (in Europe) and Aruba, Curaçao and Saint-Martin (in the Caribbean). The Netherlands is divided in twelve provinces. Two of those are called North Holland and South Holland. Incidentally, Amsterdam is in North Holland, and Rotterdam and The Hague are in South Holland - so the most important cities of the country are actually in Holland, hence the confusion.
Holland The Netherlands Kingdom of the Netherlands
England Great Britain United Kingdom
In many languages, though, the United Kingdom is called England, and the Kingdom of the Netherlands is called Holland. Spanish: Olánda, Japanese: Oranda, Vietnamese: Hà Lan, etc. It's something we Dutch have learned to live with.
And as to why people from the Netherlands are called Dutch, while Germans call themselves Deutsch... That's a completely different story! :D
In Spanish is more used Holanda and Países Bajos. I live in Argentina, and as I know, maybe also be mentioned as "Reino de Holanda".
That is an alternative. Nhật Bản/Bổn gọi tắt là Nhật. Nước + Nhật cũng được.