I was scuba diving around South Pacific (Samoa, Tonga, Vanuatu), also Thailand and never had problems with my PADI Open Water scuba diving certification. Tour operators check your certification and that you have experience, but didn’t care much is it open water or advanced or something else. But in Australia they don’t allow you to dive deeper then 18 meters if you have only open water certification. It wasn’t big loss, as most stuff is not so deep anyway, but didn’t like how all this certification business limits your diving experience. So make sure you’ll get your advanced certification somewhere in cheaper place (like Asia) before going to Australia.