That's fine. Many large keepers only use ambient temps for their collections.

If you go with a rhp I like to place the tstat in a cable strap and then glue it to the rim of the unit. In the pic it may appear to be touching the surface of the rhp but it is not.



If you go with a bulb or che I would secure the probe to the guard you place around the heat source.

You do not want to place a tstat probe on the cage floor when using a heat source from above. If you were to place the probe on the cage floor the snake could lay on it and block the heat from reaching the probe and make the tstat turn up the power to the unit making the delivered temps to high.