IIRC the first Type 56 AKs were clones of their Russian counterparts and took the type I bayo that had a ring at the rear and slid over the gasblock and locked against the 2 small hooks at the underside of the FSB.
(think Polytech legend).
Then came the folding spike bayo which was at first held on by a screw similar to the SKS and was later changed to a rivet to secure it to the integral lug on the FSB. (think Polytech AKS with spike bayo).
The last one is the familiar detachable knife type bayo as used on most AKMs, which has the lug on the gas block. These are the only methods that I know of that were used for bayo attachment on the Type 56, unless you want to count the clamp on versions that are being sold by omega weapons systems as retro fit bayonets for chinese rifles that weren't originally factory equipped with one.
On a side note; some Type 56 rifles have been observed without the threaded muzzle, I recently sent off a FSB in that configuration to have a clone built (the FSB didn't have the hole drilled for the locking pin for the muzzle nut).