Upvote:4
As a citizen of Poland attempting to enter Singapore without a visa, you are required to have a ticket out of Singapore:
- Visitors are required to hold proof of sufficient funds to cover their stay and documents required for their next destination.
- Visitors not holding return/onward tickets could be refused
Staying in Singapore for the maximum permitted 90 days and returning immediately after a short "visa run" to Bali will also have looked suspicious, since this looks a lot like you're working in Singapore. Being an Eastern European female, presumably young and unmarried, will also raise suspicion that you're illegally working in the... nightlife industry.
Since your denial is now on the record, you have likely been blacklisted. Instead of attempting to apply for another tourist visa, I would advise that you apply for a visa that matches the reason you want to stay in Singapore that long: LTVP, employment pass, etc.