I think I have seen ppl reporting in the other post that Singtel Hi does not provide Voice/SMS roaming, while the common postpaid is eligible for those (though very expensive). And the customer support is different.
Not sure if there is any more difference between the Hi and the common postpaid
1) The main thing is that Priority may be different between SingTel 5G+ (S$15.28 plan) versus SingTel hi! 5G+ (S$15/20/25 plans), and between SingTel 5G+ Enhanced (S$19.25 special offer, S$35/40 plans, or S$24.5/S$36 now with port-in offer) versus SingTel hi! 5G+ Enhanced (S$35 and S$35 plans).
There are no SingTel hi! PostPaid plans with 5G+ Priority label.
2) Billing wise SingTel SIM Only has prorated billing and it is monthly based. SingTel hi! PostPaid is 30-day based billing and no prorated billing.
3) Then "hi! by SingTel" PostPaid plans do not support the following features.
Note: the first one may not be clear, you should still be able to receive free incoming SMS if you have active roaming data plan when connected to overseas 4G LTE and 5G NSA network as per the reports.
https://www.singtel.com/personal/products-services/mobile/hi/hi-plan-faq
hi! Plan does not support these features:
• Roaming calls and SMS services are not available while overseas. However, you can still receive OTPs in destinations that support 3G networks.
• Outgoing local calls to 1900 numbers
• Incoming and outgoing video calling
• Incoming and outgoing MMS
• Outgoing Global SMS
• Transfer of ownership
4) In the end, if you need the roaming benefits from Singtel hi! PostPaid, or Gomo, or Zym/Zero1/VIVIFI/CMLink, just go ahead to try it out.
You can also stick with SingTel SIM Only, but add eight/Max/SIMBA as secondary line for roaming and backup, if you are willing to pay two lines.