Hotelstorm spend $200 or more and get $50 back.
in one transaction online only.
it says for every transaction, so most likely can be used multiple times.
Terms and conditions:
* Check the applicable cancellation policy for your reservation prior to making payment, as some reservations are non-refundable.
* CommBank American Express Cards: If you hold a CommBank American Express Card, and you register for an offer with American Express Connect, you’ll need to make a qualifying purchase with your Card before 31/10/2018 to receive the credit to your Card account. Click here to find out more about changes to your CommBank American Express Card.
* Only spend on this Card counts towards the Offer.
* Excludes transactions where you do not spend directly with your Card to which the offer is saved, online at HOTELSTORM (Agoda partner) at www.hotelstorm.com/amex-au. Offer valid at Australian website only.
* Excludes transactions made through a third party establishment or payment processor.
* Credit is not redeemable for cash or other payment form.
* Credit should appear on your billing statement within 5 business days from qualifying spend but may take up to 90 days from the offer end date.
* Credit will not be applied to your Card account if your Card has been suspended or cancelled.
* Credit may be reversed if your qualifying purchase is refunded or cancelled.
https://au.trustpilot.com/review/www.hotelstorm.com
Have a read through their reviews - even the most recent ones aren't too favourable.