Most of the housing in Ho Chi Minh City, like all of the other cities in Việt Nam, is four or five stories tall.
This is true for new middle-class houses even in the smaller villages.
I understand there is some new high-rise housing in Hà Nội in the new suburban "new urban areas", but I did not get out to see them.
In HCMC, some Taiwanese investors built a new high-rise apartment complex in Chợ Lớn (Chinese) area of Sài Gòn.
Very few of these apartment or condo units have been rented or sold. In speaking with some HCMC citizens, they felt that they had not sold because the units are too expensive compared to normal units in Sài Gòn, and the Vietnamese much preferred the walk-up four-story houses to the elevatored high-rise housing.
This is certainly counter to the Chinese pattern of replacing low-rise housing in all of their cities with high-rise housing.
Interestingly, the density of population per hector or acre for these high-rises is about the same as low-rise housing since these new high rise towers are usually "towers in the park" with a lot of space (usually wasted, in my opinion) around them. I vote with the Vietnamese -- I prefer my density in active low-rise units rather than sterile units in the sky, unless the high-rises are as dense as in Hong Kong.