I have successfully redeemed my April 2018 Singapore Savings Bond (SSB). The average yield over ten years was 2.31%. I have decided to use the money and subscribe for this month's SSB (code: GX18120X). The average yield is higher at 2.57%.
If you are wondering how to forecast the average yield for next month's SSB, you can refer to the MAS website (here). Simply download the daily 10-year bond yield for the latest month. Next month's SSB yield will be the average of these values.