Not always and if someone can, it's not often. Generally, it isn't wise to try and to determine an Asian's (or any other ethnic group) race just by appearance. Factors such as name may be better for that sort of thing. Along with the matter of this question, I must input that Asians aren't the only ones with the race identifying problem. I, an African-American, have met and seen many blacks who I assumed were African-American like myself until I discovered that they were Haitian, Jamaican, or of some other ethnicity. I have also met whites who I thought were American until I discovered they were of other ethnicities such as German, Italian, and Dutch. This even occured to some Latinos in my community who have assumed to be Mexican when, in reality, they were Puerto Rican, Guatemalan, or Dominican.