Vietnam or Singapore Airlines to Hanoi?

[nj12]

SQ will through check baggage whether single ticket or separate tickets if SQ >> SQ

If you mean SIN-SGN such that it is SQ >.VN, then yes as VN has an interline agreement with SQ

To clarify, the whole return leg is CGK-SIN-SGN-MEL with CGK-SIN-SGN on SQ and SGN-MEL on VN (Transit only). Would SQ check the baggage all the way through to MEL given the flights are on separate tickets with separate carriers? I don't plan on clearing immigration in SGN unless i'm required to in which case I will need to book the earlier SQ flight into SGN to account for long immigration wait times.

 

[Quickstatus]

whole return leg is CGK-SIN-SGN-MEL with CGK-SIN-SGN on SQ and SGN-MEL on VN

Technically yes SQ will through check to VN for SGN-MEL flight as SQ has an interline agreement with VN. Additionally some SIN-SGN flights are actually codeshare with VN
Each baggage tag can also hold 4 consecutive sectors which is what you have

However the problem arises if something happens to the SIN-SGN flight causing you to miss your SGN-MEL flight. In this situation, you may have to enter Vietnam. This requires a Visa which is required to be purchased before departure to Vietnam

Some suggest buying a Vietnam visa just in case