I am not sure Dogfighter2111 is talking about Singapore Changi Airport - sure does not sound like it.
You will notice that on your IFE screen near the end of the Jakarta-Singapore sector, a list of connecting flights will be displayed with their gate numbers. You will also see the gate your flight from Jakarta will dock at.
Just let the crew know in advance that you have a 50-minute connection, and chances are that they will bring you to a seat near to the door just before landing in SIN
, and ensure that you get priority when de-planing.
Once you exit the aerobridge, just check with the ground crew for the direction to the gate where your connecting flight is.
In all, a breeze . . . so no worry. As Pilatusguy said, even a 20-minute transfer is not impossible.