If the tub is only 3 holes for faucets, Is it possbile to drill another hole for the shower bath pocket without destroying itself? A plumber can do and will expensive?

If I understand correctly, you want to add a shower head on a soft line to your spa? A plumber can do that, but I think you might have trouble find one that does. Most plumbers will not install even a stick flex on a conventional shower because the plumbing codes to prevent the increase ties and incidents of refoulement Yes, you can get these pieces in your local hardware and install it yourself, but anyone What plumber willing to ignore code a little money will not you or your family any favors.