A new ring may be certainly possible in this case. But usually one does a compression check on the engine cylinder. If the compression is low, you squirt in a little oil and check again. If the compression goes up, then you need a ring, if the compression doesn't go up, then it is the valves need work.
They do make compression gauges for glow engines too.
But one can get a ring and install it and see what happens, the ring does cost less than a compression gauge and you can get the same results as to whether it works or not.