The timing question first
Search this and you get exchange and broker pages: contract specs, margin, how to open an account.
Those answer where to buy it. What most people actually want to know is the other question: do the hours fit the life I have in Singapore.
That one is easy. Singapore and Malaysia are in the same time zone, and neither uses daylight saving.
So the session table we have already written needs no changes for Singapore.
The Nikkei has suitable windows in the morning, the afternoon and the night. Which hours exactly is in this one: Nikkei JPN225: which hours suit trading in Malaysian time?