You have benefited from the sound input of attyLLL and melki, and also by HR adviser no doubt.
But not paying your crew overtime? thats gonna raise a lot of problems man. from admin to legal.
Advice lang po ito, perhaps you can try a more positive approach/motivation for them to come on time simultaneous with the stick approach? You should definitely issue them NTE's, but make sure you keep ALL the records intact. For paper trail. Especially if you pursue the "habitual" track. Kapag walang DA or NTE yung tao mo for the past years, then suddenly you issue a DA or even termination of service stating "habitual", medyo questionable yan. But you have the right, of course. Peace!