A $3\times 3$ Lax Form for the $q$-Painlevé Equation of Type $E_6$

For the $q$-Painlevé equation with affine Weyl group symmetry of type $E_6^{(1)}$, a $2\times 2$ matrix Lax form and a second order scalar lax form were known. We give a new $3\times 3$ matrix Lax form and a third order scalar equation related to it. Continuous limit is also discussed.