Is it the same frog? Maybe you have a large population that keeps wandering in? They're attracted to bugs that are attracted to light, so maybe that's why it likes your house.

You're right, it's probably a good idea to make sure it stays outside so it doesn't dry out or get stepped on. It may help to move it further away than your herb garden. If there's any source of water around nearby, move it generally in that direction.

If you decide to stop trying to keep it out, maybe put a shallow bowl of dechlorinated water on your floor. (You can get dechlorinating solution where ever you can buy stuff for pet fish.) If you decide to keep him as a pet, I've heard you have to have a license to keep pet frogs in Australia.

Edit: I don't know much about Australian frogs, it could be a Leaf Green Tree Frog?