I replicated the same scenario on my end, Nagakambing.

It automatically converted into US dollars when I ran the Profit and Loss report. 

We can check if this is a result of a damaged company file. Let's open a sample company file and record these transactions there. We can run the verify and rebuild data in your company file if the Profit and Loss report in the sample shows the correct details.

You'll want to uninstall and reinstall your QuickBooks Desktop if you'll experience the same behavior in the sample file. This resolves any error in your QuickBooks Desktop.

Feel free to post again if there's anything else you need help with multi-currency.