...not "ROWAN & MARTINS LAUGH-IN" since Dan Rowan and Dick Martin weren't the hosts, this was justtitled "LAUGH-IN" and ran on NBC in the late 70s. It used the same format as the first one, but didn't have a regular host.
Remember it?

I think Robin Williams was a regular on it.

It was a series of specials during the 1977-78 season that NBC reran on a weekly basis briefly in the summer of 79, at that time predictably playing up Robin Williams' relatively minor presence.

ISTR George Schlatter sued the network for rerunning it as a weekly series; don't recall why.

I definitely remember this. Can't say I remember much about it, but I know one of their "regular" sketches included commercial spoofs, and one I remember was with a Latin woman who was a commercial spokesperson for "sugar" and also a brand of toothpaste, and she was always chugging from a tequila bottle.

i remember one of the promos from 1979 showed robin williams saying in a high pitched voice over and over again i am ton a tuna i am not a tuna

I remember the short-lived revival of "Laugh-In". It was an attempt to bring back a ground-breaking show that was a big hit in the late 60s and early 70s but it wasn't as good. A lot of the regulars were unknowns, including Robin Williams. There was also Lenny Schultz. The animations were done by Mad Magazine's Sergio Aragones and streamed across the screen.