Japan has contiguous maritime boundaries with Great Neighbors such as the Russian Federation, and the People's Republic of China, South Korea and North Korea. Yet there has been no war or conflict with our neighbours in 70 years. How do we do this? Simple. Maintain a pragmatic foreign policy. War is never necessary and differences can be meted out through diplomacy.
Japan had a very nasty history with China, given we fought a long war with them for over 14 years, it was a brutal war on both sides. Yet despite this, both China and Japan are able to divorce historical differences , and in the spirit of mutual development and growth of East Asia, Japan and China have put differences aside. We've never had any major conflicts since then.
Vietnam can learn from our strategies. Your fatalistic zero-sum mentality is not productive and is too narrow minded , it prevents you from adopting a pragmatic approach with neighbors. You write about China's abuses, advances. You complain about China's imperialist ambitions, that's fine and all and i am sympathetic to this. But at the same time, when you impose your will on others and excuse conquering other independent nations (Laos, Cambodia, Thailand) to create a 'Submekong Empire' is quite hypocritical of you. You are being something that you opposed and claimed true about others.
Open your mind, friend.