Weird thing is, I saw Sam Jones promoting the movie on Nickelodeon's teen oriented talk show LiveWire at the time, and I didn't pick up on any vocal disparity with the clip they ran. (I think it was the football with Ming's men scene.) When I saw him decades later on the SciFi channel series, his real voice being different was obvious.
It was really funny when an audience member got the movie mixed up with Flesh Gordon. Wish there was clip on youtube!