  We propose a simple theoretical model referred to as the {\it two-band model}
to realize both a large Seebeck coefficient and high electrical conductivity,
resulting in a high thermoelectric (TE) power factor ($PF$). Using the
Kubo--Luttinger linear response theory, we apply this model to the TE response
of an FeSe thin film reported by Shimizu {\it et al.} to show a high $PF$ with
strong temperature dependence. The effects of superconducting fluctuations and
excitonic correlations are found to not be critical.
