You can always consider the following.
I am considering #2 or #3 or #4 for my second S$15.28 line which got rejected for the recontract order.
1) Singtel MVNOs like Zym, cheaper and with more roaming data. Zero1, VIVIFI and CMLink are similar.
https://zym.sg/
S$10.10 4G plan, free three month and free 5G forever for non-Singtel port-in,
S$11.10 5G plan, three months S$10.10 OFF for non-Singtel port-in,
There is a trick to port to MyRepublic or Maxx first and then port to Zym to enjoy the non-Singtel port-in benefits.
2) Singtel hi! S$15 plan
3) M1 Maxx S$12 plan
4) Starhub Prepaid S$15 plan
5) ...