The best day to arrive at Singapore is Saturday and it would be best to avoid Sunday, as prices are on average 31.59% higher than on Saturday. (Average prices, based on 2019 datapoints.)
The cheapest airline flying from Singapore to Tokyo is Japan Airlines. They are 19% cheaper than Singapore Airlines. (Average prices, based on 203 datapoints.)
The best time to fly is at around 0. (Average prices, based on 582 datapoints.)