Yes, THAT Keith Laumer. I grew up reading and rereading his James Retief: Ambassador to Space stories and other novels. My first really successful R/C plane was a slightly enlarged version of his .020 FF "Buttons" with ACE pulse propo with the small Adams twin actuator and a Baby Bee in the nose.

I don't know about Laumer as a painter of SF scenes, but his novels were often graced with covers painted by an artist named Chesley Bonestell.