But when you got married in HK, you also had to prove your were divorced/single, right?
This is their law: Before getting married, you have to submit sufficient evidence for your marital status. If you are divorced, you need to provide a sealed certified copy of the court’s final divorce decree, translated into English if necessary. So your Canadian civil registry should have provided this and/or a letter of non-impediment.
If you travel to Singapore, you get a card on the plane you need to fill in. This embarkation card is currently being replaced by an electronic version btw.