"Do you feel Thai or Vietnamese?"
After a slight hesitation, "Both."
Fair enough. If there was a shooting war, however, which way would his rifle be pointed?
At the other end of Thailand, there are 64 Chinese villages, populated by descendants of Kuomintang soldiers. Thailand let them in to be a buffer against the Chinese, then Thai Communists, and all have been granted citizenship. In a 2015 New York Times article, a 47-year-old man is quoted, "I may have a Thai ID, but I'm Chinese. My family is Chinese, and no matter where we go, we're still Chinese."
After seven decades, these "Thais" are still attached to China, unsurprisingly, although it's still ruled by the same Party that tried its best to kill off their forebears.
Ethnic and race mixing, though, can only go so far, and even if universally applied, will only create new shades, each with its attractions and repulsions, not to mention a lingo that's inhospitable to outsiders. With each group defining itself against all others, conflicts will continue to erupt, as they always have.
Just as a man who claims to love all women, loves no woman, no one is remotely capable of giving a damn about everybody, no matter how much he may go on, often with righteous, vindictive rage, about universal brotherhood. With self-love as his compass, he will jab, kick and snipe at all those who differ even the slightest from himself, as testified by the comment stream following this very article.
With population and sense of entitlement constantly rising, against resources rapidly depleting, a state of constant war, nearly everywhere, is the best we can hope for, and in such a situation, a fragmented society will have no chance.
Everyone's barbarism will flower.