Flight Changi Airport departs from Singapore Changi Airport at 22:10 and arrives at Tokyo Narita International Airport at 06:20.
The flighttime is about 7h 10m. The distance travelled ("as the bird flies"): 4385 Km. So the average speed is roughly 612 Km.
There is an 1 hour time difference between Singapore and Tokyo
The best day to arrive at Singapore is Saturday and it would be best to avoid Sunday, as prices are on average 63.61% higher than on Saturday. (Average prices, based on 494337 datapoints.)
We have a lot more statistics for flights NH 844 and between Singapore and Tokyo.