There is only one sure fire way and that is to charge extra for electric, You watch the guest turn it off then,
Tourist just don't get it they will have the A/C running with all the windows and doors open, I even tell them the garden doesn't need cooling down they are tropical plants.
Also getting them to turn it off when they go out is another problem that is just complete waste, there is a few things you can do, install a keycard system so when they take the card out the electric goes off.
These multi billion dollar A/C companies could help by designing a motion detector if no movement it goes of after 15 minutes, I did write to LG about it, No they don't have,
Maintenance of the A/C unit is important but Im afraid it's not high on the agenda with Thai's as long as it's still running that's ok,
Certain nationalities which I've noticed have the place like a fridge.