In your place, I would be very careful making any such statement in public (including writing anything over internet), especially when you are in Singapore. Singapore, if you probably are not aware, does not allow additional citizenship for people who got them after age of 21. There is more than enough information available about this - just google.

And yes, when it is time to have your Singapore citizenship renewed, you should do it inside Singapore and not at overseas missions, otherwise you will have to answer a question how you can stay that long in a foreign country without having valid visa in your Singapore passport. But even if you come to Singapore to renew your passport at ICA you have to answer a question in the application form if you have other citizenship(s).

And oh yes, if you are male and have not done NS, you'd better do not come to Singapore at all, because you are guaranteed to put in jail. There were multiple high publicity NS defaulter cases in recent years the most recent one is with the author of Crazy Rich Asians.

Above. If you are quiet and have stuff well-planed with reasonable explanations, it is possible to have Singaporean citizenship in addition. But I doubt that it will last for forever. With Big Data and IDA plans, one day one can get really nasty surprise...