Here's a community wiki to add to if there are more than these two:
Embassy in Hanoi, as expected:
- 46 Hoang Dieu Rd, ☎ +84 4 3845-3736.
Consulate in Ho Chi Minh, as expected:
- 175 Hai Bà Trưng, District 1, ☎ +84 8 3829-2463, fax: +84 8 3827-5845
These first two answers are from Wikivoyage. I went through each page for each city in Vietnam and did not find any others. But you never know ...
The Wikipedia page on Chinese embassies and consulates around the world agrees that these are the only two.
The "Embassies > Asia" and "Consulates General > Asia" pages on the Chinese Ministry of Foreign website also agrees these are the only two.