When I got a tourist visa to Singapore, my passport was frozen. Is it because I didn't bring my return ticket, and I didn't bring it out when I booked it? ...

The entry visa issued by China (Singapore) Immigration Bureau clearly states that if the visa requirements are not met, it does not mean that you can definitely enter the country. The rotating officials of the airport immigration office can refuse those who do not meet the requirements, and netizens may be refused entry because they do not have a return ticket.