Where in heaven’s name did you find a 44 lb chicken?
We really don’t have a lot to offer. We know that a shawerma or shewarma or shwerma is of Middle Eastern origin, featuring meat marinated and layered on a large skewer rotating around a vertical gas fire, not unlike the preparation for the Greek gyro. And indeed, like the gyro, most shawarma recipes we’ve seen use lamb (or beef).
We have no idea where you’d get a rig capable of holding that much chicken in this country, much less in Thailand (where the questioner lives). Many outdoor grills in the US include horizontal rotisserie units, but not with the capacity you require. A lot of ingenuity is invested in constructing home-made smokers for various barbecue preparations in the US, especially in the south. You might have to put the same kind of energy into constructing your own large-capacity shawarma-maker.
Have you thought about talking to Ron Popeil?