Do I have to give you the lecture again? Nobody will share military satelites with Vietnam, not for sanction reasons, but they are just not that into you.
You need military grade sats to actually be able to hit the target. Sure GPS' civilian functions are pretty good, but using that to target, and you may as well just use the missile as a firecracker, it's just as good. Not to mention, to date, people don't like to share those sensitive tech anyways even without the risk factor.
Then there is the fact antiship missiles need good radars, we have ASEA AEGIS radars, you don't, we have some of the best radars on land and in the air, you again, don't. So we will see you, but you won't see us, how can you fire any missile.
Only weapons like the HJ-12 and Javalin are sure fire ways to deal with tanks, sort of, and you got none, manpad will only scratch a modern tank, btw, unlike reports, we have close to 4000 modern tanks, while surprise surprise you have none. Again, data link play a key role, other players on the field like helicopters, infantry, sats, UAVs, fighters, and more can locate a target and share the location with our tanks and take you out, while your people still has to manually turn the gun.
China can very easily destroy the Vietnam army, you are way overestimating the Vietnamese military.