Hello Slowersloth,
Welcome to the Microsoft Community and enjoy the time you've spent sharing detailed information. I understand that the problem is that Powerpoint 2021 keeps the selected text selected when retyping it in Lao font. If my understanding is wrong, please correct me in the answer. I am pleased to offer you assistance on this issue.
We fully understand the inconvenience the issue has caused and that the current situation can be frustrating.
According to your description, we also need to confirm the information for further troubleshooting, in order to better help you solve the problem.
Are you having this problem only in the PowerPoint application? Have you encountered the same situation in other office applications such as Word?
Does this happen to all PPTs when you are editing in PowerPoint 2021? Or exists in some specific PPT document?
Have you checked your office for updates? If so, please update first.
Secondly, it is recommended that you open PowerPoint in safe mode to see if the situation persists, as it may be some add-in that is causing the problem. You can click here to learn how to enter Safe Mode.
If this situation still exists in safe mode, it is recommended that you perform an office repair, which may solve your problem. You can click here to learn how to repair office applications.
We have to go through a series of steps to find the real cause of the problem. If the above steps do not solve your problem, please let me know and I will continue to help you with the problem.
Sincere greetings
Mavis - MSFT | Microsoft Community Support Specialist
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