100% agree due to own experience, what Chinese people told me themselves, and what I see on YouTube... While Chinese in Hong Kong, Taiwan, Malaysia, etc., are cultured and polite people, the same cannot be said about mainlanders. (Obviously, the Cultural Revolution, and 75 years of CCP rule have killed off most of Chinese culture and manners.)
Why the admiration of (mainland) Chinese in Thailand? Who knows, but I blame brainwashing of the masses by the Chinese-Thai elite and media.