No one really knows why it's behaving differently in Asia in general. I do have several friends who work for NHS in the UK. They tell me that in their ICU wards the majority on the ventilators are in fact SriLankans, Indians, & Bengalis.
The Indian doctors have a theory that all these migrants have been in the West for many years (20 to 30 years or more), they miss the Sunlight and hence Vitamin D deficient. It's probably true and the established fact is that those who are low in Vitamin D are the first to go. Vitamin D plays a part in respiratory diseases in general and could have some protective effect on Covid 19.
The Asians say, they have stringent lockdowns in case of infection and they are used to wearing masks and adhere to Covid measures thoroughly because of their past bad experience with SARS. Also their everyday greetings are mostly non-contact.
OTOH the Japanese scientists have noticed that with their patients there is an abnormality in the IgG counts. When we are infected with a bug the first thing that happens is, we develop an antibody called "IgM" to defend ourselves. A few days later, when the immune system is geared to this first attack and starts to build an immune memory, a second type of antibody called "IgG" will be formed.
What the Japanese noted was that in their patients the IgG levels go up within a short time with only low IgM levels. This shows that the body reacts as if it knows about a similar virus beforehand. It's not exactly the effects of the recent SARS or MERS but they think the Asians may have been exposed to different Corona viruses over thousand years ago and we could have inherited a different immune response than the Europeans.
This is a possibility and a reality. For example Africans are better protected than the Europeans for some types of Malaria.
A Japanese team is working on this and they have found that there is a difference in the HLA (Human leukocyte Antigen) types of the Asians and the Caucasians. It will take some time to establish whether there's really a racial factors affecting the Covid outcome. This team is headed by the Japanese immunologist who was awarded the Nobel Prize in 2018. So it's in good hands.
This is all that currently known other than some still believe that the old BCG might have an effect. But this isn't proven either. With Covid the unknowns still far outweigh the knowns.