  A simple single folding model for $\Omega$-deuteron with maximal spin
$\left(I\right)J^{P}=\left(0\right)5/2^{+}$ is investigated. $\Omega$ is
assumed to orbit an unperturbed deuteron in a $\Omega$-deuteron potential based
on a separable $\Omega$-nucleon potential from lattice QCD. We show that the
effective central folding potential of $\Omega d$ in the $^{5}S_{2}$ channel
has a simple Wood-Saxon form, and approximate the upper bound for the binding
energy of $\Omega$ particle on a deuteron. In order to investigate how changes
in the wave functions affect the results, we consider four analytical forms for
$S$-state deuteron wave functions, i.e., two widely used Hulth\'en forms, as
well as the modified Reid93 and Argonne v18 forms. Our calculations of binding
energy from simple two-body approximation are compared with the results
reported for the three-body problem; it is confirmed that the $\Omega d$ system
is deeply bound. Although the single folding model reduces the three-body
problem to a two-body problem, this simplification is inadequate.
