The original Vietnamese characters which was based on Chinese Characters like Kanji was abolished by the French. Unfortunately, it would require too much effort and time at this stage for Vietnam to try to revert back. However, Vietnam should make it an elective subject in High School like South Korea. At least the traditional characters are still used in the ancient Temples in Vietnam.
I think Vietnamese females can be quite similar to Japanese whereas I strongly think Vietnamese males are more similar to Korean because they are often a bit aggressive and prone to violence and crime. I say this as a Vietnamese man who has had many Korean friends. Of course there are many Vietnamese males that are similar in nature to Japanese too. But there is a reason Vietnamese gangs are a bit of a stereotype around the world☹️
The Thai women you are referring to are of Chinese ethnicity. The largest Chinese diaspora population in the world is Thailand. They have completely assimilated with Thai names and can only speak Thai. Estimates are 20 to more than 30 million Chinese. This is why many Thai look similar to Chinese, Japanese and Vietnamese. But in fact, ethnic Thai people look a bit different to us. As a reference, just look at the Thai kickboxers that fight in Japan, they are darker skinned and look typically “Southeast Asian”. Sorry, I’m from Australia so I can only speak English🙏