Latest update from a friend who went this morning.
1. SG has visa-free travel like before.
2. PCR/ART: Staff at Changi departure gate will ask you for PCR test - some vietnamese friends said ART is enough. To be safe, please take a PCR test and print out with PDF.
3. Health declaration
https://tokhaiyte.vn/ - can be done online before reaching, or when touching down in VN.
4. PC-Covid app: I think this is for vietnamese - I'm not sure if visitors need to download any app yet. I will be going on 19/3 so let's see.
5. No quarantine required