Is the right ventricle muscular walls thicker than the left?

No.

The wall of the left ventricle is much thicker. The left ventricle pumps blood through the systemic circuit, which travels though the entire body, excluding the lungs, returning to the right atrium. This requires overcoming the various resistance factors within the blood vessels including, but not limited to, distance traveled by the blood, gravity, and vessels with a narrow radius. To generate the necessary pressure, the muscle, or "wall" of the left ventricle, is much thicker, and therefore much stronger.

The right ventricle pumps blood through the pulmonary circuit (to the lungs and back to the left atrium) which is much shorter and less complex, and therefore requires much less pressure and far less muscle.