Please don't be offended by this...?

probably chinese...Japanese(in particular) and Filipinos are quite obsessed with showering and personal hygiene. China is the only east asian nation where body odor and habits like spitting in public, pushing mucous out of nostrils onto sidewalk etc in public exist. It's obviously not ALL of them! But their level of cleanliness in general is lower than other east asian nations.

I have been in the company of Asians, and they are not unclean people. Your assumption about them not showering is implausible.

However, there is one possibility that I can think of.

If this is your first encounter with a large group of Asians or, perhaps, a location where Asians predominate, when you are typically with a culturally different group of people (even culturally different Asians), then it is likely that you are unfamiliar with their natural scent.

Sort-of natural.

See, if my knowledge is correct, all humans have scents and odors, and, generally (or perhaps simplistically), these scents and odors are majorly related to the individual's diet. So if you are in America, and you know all these Asians in America, and you all go out and eat burgers and hotdogs and pancakes with syrup and coffee and steak and broccoli and carrots and apples and oranges and the like, then all that standard American fare will become your body composition, and you'll reek to high hell of all those foods that create a generalized odor surrounding your being. Also, all your friends, Asian or otherwise, will have the same odor.

The result: Nobody notices it.

Then, suddenly, you enter a new environment. Some different country, maybe. And everybody eats slightly different meats (especially animals raised on different plants etc) and different vegetables and fruits and sauces and seasonings. And you walk into a massive group of those people- they'll smell weird. They will have a noticeable and pungent odor that is natural and vastly different and possible repulsive to your tender senses that are so used to burger and fries body odor.

And if you are with a group of your own people, they WILL think that you smell for these reasons. They would be as unfamiliar with the scent consequences of your diet as you are with theirs

Once you have become better acquainted with that odor, you will likely quit noticing it, especially if it becomes a constant in your life. However, the odors are always there, surrounding all of us.

And so, finally, if these Asian people are foreign or if they are in an environment that is largely composed of them, specifically, then their unfamiliar diet-related body odor may affect your foreign senses - at least for a time. And even if these people are Americans and have a fairly America diet, it is likely that they eat lots of different sorts of food at home that their grandmother prepares or whatever. You know, those Asian grocery stores are in every city. Asians shop there and cook that foreign food to their hearts content, even if they have no choice but to eat American when they are dining out with you. So, it is, unfortunately, quite natural and unavoidable that sometimes body odor can be so repulsive. However, this smell would occur even if they showered every 15 minutes.

They are probably asking the same question about you...why does that guy stink?!?