When it's 11:00 AM in Singapore, it's 10:00 AM in Hanoi.
Vietnam is one hour behind Singapore year-round. Neither observes daylight saving time, so the offset is constant.
Quick reference:
| Singapore | Hanoi |
|---|---|
| 11:00 AM | 10:00 AM |
| 3:00 PM | 2:00 PM |
| 9:00 PM | 8:00 PM |
Flight time between the two is ~2h 30m—so you'll arrive before you "left" by the clock!