Your questions about SoFi Hong Kong are answered here

You have full control. You need to switch off your monthly direct debit setting at least 3 business days before the 15th of the month.

In order to do so:

Under Auto Invest, select your investment portfolio Under “Monthly Contribution”, tap onto your current US$ amount. Toggle “Activate Monthly Direct Debit” to off. Hit “Save” at the bottom of the page.

If you wish to resume making monthly contributions, you need to re-activate direct debit following the steps above while toggling “Activate Monthly Direct Debit” to on.