Flight Changi Airport departs from Singapore Changi Airport at 22:50 and arrives at Tokyo Narita International Airport at 06:45.
The flighttime is about 6h 55m. The distance travelled ("as the bird flies"): 4385 Km. So the average speed is roughly 634 Km.
There is an 1 hour time difference between Singapore and Tokyo
The best day to arrive at Singapore is Sunday and it would be best to avoid Friday, as prices are on average 130.25% higher than on Sunday. (Average prices, based on 508001 datapoints.)
We have a lot more statistics for flights SQ 636 and between Singapore and Tokyo.