Why is access to Asia usually made from Singapore?

Question

Startups

Hello everyone
Now I am studying the issues of entering the Asian market, I am faced with the fact that many bourgeois companies first open offices in Singapore, and only then open their paws to China, Korea, Japan and Indonesia.
Question: Why is Singapore so attractive?

Answer 1

In short
For the sake of interest, here is a complete fresh report for all countries
p.15 - General summary table ("Ease of doing business ranking")
p.196 - By country in alphabetical order, brief tables for all indicators ("Country Tables ")

Answer 2

There is another option to try through Thailand. But they need a local co-owner.

Answer 3

I wonder what kind of product or service you want to go there with, isn’t everything there yet?