I does suprise most people that Capsicum Chinense doe not come from China, it is from the Yacatan Peninsular, Mexico.
Chillies came to the Far East later than most other parts of the world migrating East from India. With these countries having lemon grass, ginger and galangal, which were very complementary to the chillies. The new spice was very popular as was far more fragrant than the native Sichuan Pepper, which is more a seed than a fruit.
Enlongated, hot or very hot peppers that pointed upwards were the popular option, hence Capsicum Frutescens is the winner!
So many dishes are chilli focused and the hotter the better, to the point that people challange each other constantly.
Thai hot is a favourite, which is quite misleading as there are 79 varieties of Thai hot, nevermind starting to count the varieties of Birds eyes peppers, which are smaller than Thai varieties. Moving to Indonesia and the islands, they share the same taste, but have a few milder options due to the Portuguese influence. Japan did not follow this new spice fruit, choosing to trade sugar in its place.
I have yellow and orange birds eye, Thai dragon and Khang Starrs varients of White Thai growing this year.