Seriously - this is one weed where you have to "think like the weed" - as it is capable of appearing in the most unlikely places. Its ability to send runners under often quite dense vegetation and garden plots, and the possibility that these runners can become new infestations, means we have to be quite diligent in searching them out. This is particularly true of beach infestations - where native vegetation can conceal quite extensive infestations of Singapore Daisy.
We are so lucky that it is not a prolific seed producer - but it does produce some seed. This becomes evident when controlling beach infestations, as a period of heavy weather can wash seeds and fragments of Singapore Daisy onto your nice cleaned beach. Maybe you will have to locate upstream infestations - and try to help the owners to get rid of their infestations too. Controlling upstream infestations is really important.