visa

Hello

We will be doing a cruise starting in Hong Kong and ending in Singapore. One of our stops is a day stop in Ha Long Bay, we would like to go to Hanoi but for one day round trip is too much travel so we thought we would go to Hanoi, either overnight there and fly to Da NAng the next day and meet up with the ship there or take the night train to Da Nang.

Would we need a separate visa or would the one we get on the ship be ok for this?