Reverse Charge Mechanism (RCM) on online membership purchase

Hi,

Recently I have purchased a software membership of $170 from a Malaysian website. The website didn't provide any invoice, except an auto-generated payment receipt.

Do I really need to raise a self-invoice applying the RCM and pay the 18% reverse charge GST? Or, can I just raise a self-invoice without applying the RCM? Or, Can I just show it as an expense?