Yes. Many radio flash triggers can be fired directly from the camera’s hot shoe and do not require a sync cable. For the CowboyStudio NPT-04 specifically, the transmitter can be mounted in the hot shoe, so you use either the hot shoe or a sync cable—not both.

More generally, most basic manual radio trigger systems are designed to work this way. The sync cable option is usually just an alternative for cameras or setups that use a PC sync connection.

Examples mentioned by users that commonly work via hot shoe include Cactus, Phottix, PocketWizard, Yongnuo, and RadioPopper models. Compatibility can vary by brand/model, so check that the transmitter physically fits and is compatible with Pentax hot shoes.

Since your concern is the old flash’s high trigger voltage, keeping that flash off-camera and firing it through a radio trigger is the right idea rather than mounting it directly on the camera.