For Thailand and Philippines, I don’t consider them to have truly assimilated. A few really do, but I think most take on a new identity (e.g. Tsinoy) and identify them as being superior to the locals, so I would not consider that as being assimilated to the local society.
In the Philippines, there are two groups of Chinese groups, i suppose. The pure blooded Inchik (Chinese) who marry only Chinese and presere their family names and their religion. They maintain this through the generations even go as far as going back to Fujian or Canton (Guangdong) to bring back a wife back. The other group are the mixed Chinese-Filipino (Malay-Chinese mix), who tho are not pure blooded anymore, still hold some kind of allegiance to their Chinese lineage. It is almost a sense of pride for these Chinese mestizos to have Chinese 'blood'. Its actually very interesting to see this when i was there.
During the 60-70s, a lot of pro-mainland Chinese diaspora in VN became spies for the CCP. Also, you trying to tell me Pol Pot and his crony was apolitical? The communist Chinese diaspora in Indonesia before the purge was apolitical? You must be joking.
But being political or apolitical was not the point. When I said pro-mainland, I mean Chinese who still show affinity towards mainland China and have no loyalty or allegience towards their host country. The point was that these pro-mainland Chinese diaspora have given a very bad image of “China” to the locals, by being extremely greedy, selfish, ungrateful, etc.
I think that is just part of the innate nature of Chinese people, my friend. The sense of Han superiority and Han preservation. Even in Japan; there are Han Chinese who live in Japan , even have Japanese citizenship, and have even adopted Japanese names, still, they will clarify that they are Han Chinese by Race.