It depends on what you mean by Vietnamese beauty.
Vietnamese beauty standards in the past were quite different. Men had a variety of beauty standards depending on their occupations. Men could have lots of facial hair and muscular bodies if one was a warrior, a general, etc. Men could be femininely beautiful without facial hair, had pale skin, and thinner bodies if one was a Confucius scholar, a teenage boy, a eunuch, etc. These stayed and continue to stay consistent throughout the periods.
Women, however, had many standards depending on the time periods. At one point, it was beautiful to have your hair tied up and short. At one point, it was beautiful to have your hair reaching your legs. At one point, it was beautiful to have your hair wrapped in a turban. However, one thing stays consistent: their hair always had to be straight, silky, smooth, and black.
However, the consistent beauty standard was at the face and body. Women had to be quite plump and not skinny, which meant the women were well-fed and wealthy: a sign of beauty. Their faces had to be round, monolid tilted eyes, thin eyebrows, petit noses, full red lips (from paan), full earlobes, black-colored teeth (from dyes), and 12cm necks.
One of the Four Beauties of Hanoi during Nguyen dynasty
In essence, it was a Buddha face with native additions and East Asian beauty standards.
During French colonization, however, beauty standards began to change and was more Westernized, as evidenced by the Imperial family.
Empress Nam Phuong of Nguyen dynasty
And her son, Crown Imperial Prince Bao Long
Modern Vietnamese follow East Asian beauty standards just like they did in the past. Men can have varying looks. One can be rugged and manly and be handsome, and one can be smooth and feminine and be handsome.
Actor Jonny Tri Nguyen
Singer Key (S.T.319)
Modern Vietnamese women also follow the modern East Asian trend. They prefer pale white skin, huge double-eyelid eyes, full lips, small noses, straight hair (or fake curls), and thin but curvy bodies.
Model Ngoc Trinh
Singer and actress Chi Pu