Recently I had used Changi Airport as a hub to get to SriLanka. I used separate airlines so was doing the transfer myself. I was also traveling only with hand luggage which makes transferring shorter and easier due to not have to collect the luggage and re-check it in ( An hour Minimum ).
Doing the transfer yourself means you won’t have access to your second boarding pass. However, if you find a Transfer Desk for your Airline inside the Airport for your next airline they will print this out for you. Make sure you keep your first boarding pass and provide your passport to get the ticket printed.
Worse case if you have to leave then come back in to Departures to get the ticket printed there.
Another tip is check if your Airline support Electronic Tickets that you can download onto your phone like Qantas
Here are a list of Terminals with Transfer desk