Russia has had a long-standing relationship with Vietnam, and continues to sell weapons to Vietnam. Russia is also close (from fear, I think) to China these days. These two relationships stand in conflict given Chinese efforts to push Vietnam from the South China Sea, which China basically claims is their territorial water.
Russia has a new agreement with Vietnam:
The agreement—signed on the sidelines of the seventh Moscow Conference on International Security—set out the details of military cooperation between the two countries from 2018 until 2020. Gen. Ngo told Shoigu he was pleased that Russia and Vietnam were taking steps to increase their military and naval coordination.
That's a really short road map.
It could just be about cash-strapped Russia getting another arms sale to Vietnam.
But maybe Russia is just getting ready for a Plan B in case China doesn't renew the 2001 Russian-Chinese treaty suspending territorial disputes that can be ended in 2021.*
If Russia really needs a Plan B to distract a more hostile China, selling submarines to Taiwan would be the way to go.
Of course, if Russia really needs a counter-weight to a China with large (currently dormant--not permanently abandoned) territorial claims against Russia, ceasing their pointless aggressiveness in the west would be the best bet.
*And isn't it adorable that in 2005 I thought there was a chance that post-Communist Russia might yet integrate with the West?
