We report the discovery of a new Hi ring around the S0 galaxy NGC 1533 .
The ring orbits at a radius of 35 kpc , well outside the optical extent of the galaxy .
We have conducted N-body/SPH numerical simulations to show this Hi ring could be the merger remnant of a tidally destroyed galaxy .
We find no optical component associated with the Hi ring .
However , observations hint at H \alpha emission associated with the SE part of the ring only .
The H \alpha is in the form of a few very small isolated emission line regions .
The large Hi velocity dispersions ( up to 30 km s ^ { -1 } ) and velocity gradients ( up to 50 km s ^ { -1 } kpc ^ { -1 } ) in this region indicate the H \alpha emission could be due to star formation triggered by clouds colliding within the ring .