Krabi is good. Of course, Australia is good too. It all depends on what they want.
Don't write Malaysia off completely. But if you want a quite place away from hustle and bustle, I would suggest Pulau Tioman. It has a number of beaches, some very quite. I was there in Aug, and ran into a couple on Honeymoon. There is Berjaya Tiomon Resort with all conveniences and not far from the airport. There are several villages/beaches around the island. Most of the villages, except those close to the airport, on the island are not reachable by car, but all can be reached by boat. More isolated beaches or on the eastern side of the island, but harder to reach. Smaller or more distant from the airport, villages like ABC, Salang, Paya are rustic and more relaxing with opportunities for quite walks, swimming etc.