Can a Seimitsu Ls 40 able to use LB 30n bat top?
Yes, with use of the Thread Adapter.
Some Sellers include with Sanwa LB-30N, some sell separate.
i use one on one of my sticks that has a ls-40. you will need to use a ~1/4" id washer on the shaft to prevent the bat top from tightening against the shaft cover. the shaft diameter is smaller than other sticks and if you don’t use a washer it will pull on it in such a way that the stick will not work.
Shaft Covers are not usually used with Bat Tops though.
What people do is cut Shaft Cover when they want use with Bat Top.