CN buy tech from Ukraine after Soviet collapse ( pls check their carrier, warplain, missile, tank and see if they have any big different ), not mentioning CN illegaly copied lots of Soviet weapons transferred to VN via CN during VN war.
CN also buy tech from EU-US ( bough oil rig, car tech etc license from EU, US ). Everyone buy that.
CN is our threat cos their leader always willing to bow down and beg help from US to attack VN again like in 1979 (CN leader Deng accused VN want to invade the whole ASEAN in 1979). CN alone simply can not stop VN expansion to the Sub Mekong region. Thats why, when CN or US collapse, u will see VN will unify sub Mekong region in few years.