A family of Microsoft word processing software products for creating web, email, and print documents.
Hi Thong Joon,
At the time you've set the default editing language to Thai and it goes back to English after pressing Enter to start a new paragraph, it's possible that a software conflict has occurred to the Word app. It could be the reason why the settings didn't retain.
To learn more about this concern, we'd like to confirm if there were any changes or updates made to your computer prior to the issue.
Also, here are the methods that you can perform to resolve the issue with Word:
Method 1: Install Office updates. This will provide quick fixes upon updating to the latest version of Office.
Method 2: Run a repair for the Office applications. This tool is usually used if your Office apps are acting differently when you tried opening or launching it. Click here for steps.
Method 2: Run the Microsoft Office Configuration Analyzer Tool 2.2. It provides a quick scan of possible configurations that may cause the issue and gives a solution to resolve it at the same time. Download the tool here.
Let us know if your concern has been resolved.