I would advise using other cultural identifiers to show there is a commonality with real world cultures. One way to do this is to make sure that your character names fit the cultural society they grew up in. For example, if I have a character named Akira, I'm going to picture him as someone of Japanese descent, Juan would be of Spanish descent, Sanjay would be Indian, Saikia would be I. Hell, in some cases the spelling of a name may change the ethnicity I picture them in (Lee would be the European spelling, while Li is the Asian spelling. Or May vs. Mei for a girl name equivalent). This not only helps narrow to inform a general appearance in one's mind of what the character looks like, but gives them a cultural background that is woven in and brought into cultural interactions in your own world. Consider the episode "Sokka's Master" from Avatar: The Last Airbender, where the titular master, a member of the Fire Nation, trains Sokka, who is from the Water Tribe (both nations are at war). The Master reveals that he was well aware that Sokka was a water tribe citizen because he used his real name... which is not common in the Fire Nation, while Sokka is much more common in the Water Tribes (He advises Sokka to use "Lee/Li" since it's much more common in the Fire Nation (and the Earth Kingdom).).
Another way to do this is to describe the person in outfits that are traditionally worn in the parts of the world. For Eastern Asian Cultures, one good item of clothing that can easily identify them as being from your Asian cultures is the conical hat. These hats have seen use in Asian cultures as far west as India, as far south as Indonesia, as far east as Japan, and as far north as Russian Manchuria. What's more, each culture has a different name for these hats, so you can easily tell where someone is culturally from by the name they use for the hat. If they call it a "kasa" they are Japanese, where as someone who is Chinese would call it a "douli" and someone in India, it's a "Jaapi." Again, I point back to Avatar as they used several different Asian and American cultural dress and architecture to distinguish the four nations and their fictional cultures. The Water Tribe was a mix of Inuit (though more American Inuit than Russian Inuit) with some Vietnamese River Cultures mixed with American Southern Swamp cultures for the Foggy Swamp Tribe. The Earth Kingdom was a blend of Chinese and Korean cultures, the Air Nomads had South Eastern Buddhist aesthetics with monastic temples that took inspiration from Himalayan cultures like India, Nepal, and Bhutan as well as Thai aesthetics. The Fire Nation was heavily inspired by Imperial Japan, with a few nods to Hindu and Indian Culture and Aztec/Mayan cultures when we meet the Sun Warriors.