It seems they have started peeking into your house.
A netizen posted a photo of him receiving a letter from NEA stating that they have been caught smoking in the unit (and also throwing the cigarette bud outside..) in their bedroom at 12:34am.
There was earlier speculation that they would install infra-red cameras around housing estate to detect if you are smoking within your unit. Could this be a trial run?
I guess you can never be safe, even in your own home.