Visa
For citizens of Ukraine there are two options for obtaining a visa to Singapore: either get a transit visa (which will allow you to stay there for a maximum of 96 hours), or a regular visa if you plan to stay in the country longer. Now, more about everything in detail.
Transit visa (more precisely, the right to visa-free entry when transiting to Singapore) is issued at any checkpoint, but only you must have confirmed tickets and a visa to a third country, and you will have to stay in Singapore for no more than 96 hours. There is one nuance here: if you have train, bus or boat tickets to the third country or just a return plane ticket from Singapore, the transit visa will not be issued and you will not be allowed into Singapore.
Keep in mind that stopovers, where the passenger does not go through passport and immigration control, do not count. Also, most budget airlines or low-cost airlines only carry "from A to B", which can cause problems, such as not being able to get off in Singapore or continue traveling.
A regular visa is issued if you plan to stay in Singapore for more than four days. Here you should know that there is no Singapore embassy in Ukraine. The plus is that the visa is made quickly, by e-mail. However, you can't get a visa directly through the embassy - you need to use the services of intermediary firms, for example, SingaporeVisa. Their electronic multiple-entry visa to Singapore for 9 weeks costs $35.