Can I create a bulk supplier payment file in the correct format for ABA Bank in Cambodia?

What file format does your bank require? If it's CSV/XLS, you can use the exporter tool as a workaround to generate files similar to Positive Pay systems at US-based banks.

I can help you with creating a file with the correct format that can be imported in QuickBooks Online (QBO) successfully, @a-shepherd-about.

Supported file types are CSV and QBO file. First, go to your bank's website and follow your bank's instructions for how to download a CSV or QBO file of your transactions to your computer. Once done, check the format of the file. You can choose either a 3-column or 4-column format. 

A 3-column format must have a Date, a Description and the Amount of the transaction. A 4-column has a Date, Description, Credit, and Debit column.

For your visual reference of the formats I've mentioned above and other things to check, in case you'd see an error message when you import, check out this article: Format CSV files in Excel to get bank transactions into QuickBooks. 

From here, you can now upload or import the file to the QBO account: Manually upload transactions into QuickBooks Online.

Once the transactions are added to your account, match and categorise these supplier payment transactions: Categorise and match online bank transactions in QuickBooks Online.

Then, reconcile them to make sure your books are correct and no duplicate transactions exist.

I'm always here if you need more help with your supplier payment file. Let me know in the Reply section below. Have a great rest of the day!