Flight Haneda Airport departs from Tokyo Haneda Airport at 10:55 and arrives at Singapore Changi Airport at 17:25.
The flighttime is about 7h 30m. The distance travelled ("as the bird flies"): 4314 Km. So the average speed is roughly 575 Km.
There is an 1 hour time difference between Tokyo and Singapore
The best day to arrive at Tokyo is Friday and it would be best to avoid Wednesday, as prices are on average 374.02% higher than on Friday. (Average prices, based on 495926 datapoints.)
We have a lot more statistics for flights JL 37 and between Tokyo and Singapore.