How is your negotiation of TPP? Well, a complete equal relationship seems far away, though Vietnam participates TPP, unless Vietnam's competitiveness of domestic market is strong enough to fight against Japan, Australia in this TPP. I checked Vietnam's export structure, like China 10 years ago, mainly of which are primary product.
As far as I know, TPP was first established by Brunei, New Zealand, Chile and Singapore. As US's participation, it started to have extensive influences ever since. Why does not ASEAN as an entire unit to join in? Maybe you will get more negotiable strength and support.
Really, Japan's participation in TPP will affect China's international export market.