Japanese and koreans are hard to tell. But Thai are straight out just dark tone (pretty obvious actually. Difference between southeast and eastern asians). If someone looks like they havent washed their hair or dress extremely poorely, that person most likely is a chinese. Japanese and Koreans tend to be more stylish. Vietnamese are usually skinny and short or fat and acts like mexicans(same for filipinos). By personality, japanese usually are very shy, koreans are more straight forward, and chinese are extremly obnoxious when there are more than 1.

In psychology i can tell u that its not he race or ethnicity of the person that cause the "they all look the same" effect, rather your familiarity and perception. Regardless of how they look or what their skin color is, you wont remember everyobe you pass by on the street. Therefore you wont recall every single person even if you cross them again. If there are faces that you remember, that means your brain picked up some sort of impression important enough to store in your memory. So the chance is, your brain would pick up almost everyone on the street as "all the same" under the notion they hold no importance to you. If you find yourself in that situation more often for certain race or characteristics, that just mean you havent been exposed to those certain "inputs" in your life. Its sorta like how those native to english language would find spanish or french more familiar than korean or chinese, even though they might not understand a word of spanish or french.

In soviet russia, fitness trains you