monster kills ppl, & they are found with heads sticking out of swamp/clay
That's not much to go on.
The first thing that popped into my head was an hour long pilot for a show (actually the second of two pilots) which aired in 1978 by the name of The World Beyond.
A man gets sent to an island (due to having died on an operating table and now being in contact with an otherworld that steers him to supernatural happenings) where he meets with a woman looking for her brother who has been involved in the supernatural.
Long story short: the brother created a mud monster (golem) which then kills him and the heroes of the story have to deal with the monster and destroy it.
If memory serves me correctly, the brother was found dead with his head sticking out of the ground.
http://home.earthlink.net/~usondermann/mud.html
Not a swamp monster movie, but heads sticking out of the ground figure prominently in Motel Hell.
Perhaps you are mixing that with a swamp monster movie, like "Terror in the Swamp" or "Bog".
World Beyond is probably it. sounds very close to what I remember, & your link show an ad for it looking like it's made-for-tv. thanks!