The short answer: Singapore has no single national preschool curriculum. The government sets frameworks that guide what children should learn, and each centre designs its own curriculum within them. So two licensed preschools can look quite different, one play-based, another Montessori, another built around a language or project work.
That is why asking about the curriculum is one of the most useful things to do on a visit. This guide explains the two official frameworks, the main approaches you will meet, and the questions worth asking.