If you drill a hole say 10mm Diam into any pole that is set into the ground (all the way into the centre) the chances are good, but not infallible, that if termites did get into the pole below ground level they will block up that hole with their mud mixture as they eat their way up the inside of the pole. Usually they will block it at the surface but they may block it further in. Your yearly inspection will include poking a screwdriver into each hole to ensure it is clear all the way in. Up to you.