passport

Do the Singaporean authorities know that you have taken Belgian nationality?
The Belgian authorities do not notify other countries when their citizens take Belgian nationality precisely because there are countries which do not recognise dual citizenship. If the Singaporean authorities don't know, then it follows that the Singaporean passport will not have been cancelled.
On the other hand, I'm just stating what seems logical and you may not want to take the risk based on my interpretation of logic!

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