Oppo_Free_Unlock_v1.0.zip

If you haven't already, enable Developer Options and USB Debugging.
Next, download the Oppo_Free_Unlock_v1.0.zip file from the attachments and extract it somewhere.
Before you run anything, though, there's a little preparation that needs to be done.
Open Device Manager and expand the Network Adapters category.
Find your Ethernet adapter and double click it to open its properties.
Go to the Advanced tab and find the Network Address option in the Property pane.
Under the Value pane, select the radio button next to the text box and paste in the following: 704D7B61ABCD.
If you don't have an Ethernet adapter, try to find another network adapter here that has the Network Address property. It may help to install VirtualBox, since it will add fake Ethernet adapters.
Close the properties window and close Device Manager.
Go to where you extracted the unlock tools. Open Sec5.exe.
Make sure your device is in MTP mode, and then press the Unlock button.
After about a second, a string of numbers and letters should show up in the left pane. A few seconds later, "OK" should start flashing in the right pane. If it says "device not found" or something similar, make sure MTP Mode is activated. Press "Stop unlocking" and close the window.
Open the phone app on your device and dial *#3954391#. Then dial *#391#. A screen should come up with a whole bunch of regions listed. Choose this one: "Singapore Ex". Note: This Version has Theme Store, but no Ringtone Maker. Feel free to try other versions. EDIT: DO NOT CHANGE TO A REGION WITH CARRIER, ESPECIALLY THAILAND AS YOU WON'T BE ABLE TO CHANGE BACK! AT LEAST WHILE ON ANDROID 10. STICK WITH THOSE THAT END IN EX. Once you have done this, it appears that you can always bring up the region menu when dialing the numbers..
Your phone should now reboot. Once it's rebooted, your region will have changed.

Every time you changed region and want to change it again you need to use the software. You can get a code that you can use every time to change the region instead of using this software every time. (Update- one person report that this code(token) wont work for every time as his STAMP code changed.)
For this you need to: Open the dialer app , dial *#9434# ,press authtokendecrypt. You will see a IMEI and STAMP. Open the Sec5.exe and write the IMEI and STAMP shown on your phone in the blank space of the IMEI and STAMP in the software and press Generate a token, you will see a string of numbers and letters, write it on the token blank text box and click authtokendecrypt. Now you will see every text written in green. Now you can follow the steps in the guide but skip the steps that have to do with sec5. The Token that the software gave you is the same code that you need to enter in the *#9434# every time you want to change region so you do not need to use the software ever again.