An 11 am flight sounds very tight but potentially doable.
On my cruise, the disembarkation did start at 7 am. The best bet would be to do self-disembarkation and walk your own luggage off.
My flight was at 2 pm so I wasn't in a hurry but this was my experience (it may be a different experience at 7 am where potentially more people are trying to leave). We left our stateroom at around 8:15 am and exited the ship with our luggage. There was a short lineup to exit the ship. After that, we had to go through Singapore customs in the port. I think there was an issue with customs machine so I had to go to a separate line to do the biometrics again (this happened to a number of people).
After finishing with customs we got into the lineup to get a taxi. At the cruise ship terminal, the level above had an area for hired cars but we opted to just wait for the next taxi. We waited in line about 15 to 20 minutes for a taxi. The ride to the airport was about 20 minutes. We arrived at the airport around 9:40 am.
If you're flying business class with priority checkin, then the checkin should be quick. I'm not sure how long it would be if it was economy class.
So I think an 11 am flight is doable but there is little margin for error in case some issue comes up.