  The lower bound on the decoding error probability for the optimal code given
a signal-to-noise ratio and a code rate are investigated in this letter for the
reconfigurable intelligent surface (RIS) communication system over a Rician
fading channel at the short blocklength regime, which is the key characteristic
of ultra-reliable low-latency communications (URLLC) to meet the need for
strict adherence to quality of service (QoS) requirements. Sphere packing
technique is used to derive our main results. The Wald sequential t-test lemma
and the Gaussian-Chebyshev quadrature are the main tools to obtain the
closed-form expression for the lower bound. Numerical results are provided to
validate our results and demonstrate the tightness of our results compared to
the Polyanskiy-Poor-Verdu (PPV) bound.
