Flight Haneda Airport departs from Tokyo Haneda Airport at 00:25 and arrives at Singapore Changi Airport at 06:55.
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 Tuesday and it would be best to avoid Friday, as prices are on average 353.4% higher than on Tuesday. (Average prices, based on 496145 datapoints.)
We have a lot more statistics for flights NH 843 and between Tokyo and Singapore.