Hi ​@Pongdej Saovapakhiran, Thanks for letting us know about this!

I tested it out, and I'm seeing the same thing – the issue happens when text style names use Japanese characters.
Could you tell us the name of the style where you're seeing this?
 

Here are the steps I used to reproduce the issue. If you're doing something different, could you let us know the steps you're taking?

1. Open a slide deck.
2. In the Design tab on the right sidebar, navigate to the "Template style" section.
3. Click the down arrow icon to open the style list.
4. Create a style with a name that uses Japanese characters.
5. Add a style - Click the + icon to open the "Edit text style" modal.
6. Edit the text size.
7. Notice that in the list, the style name using Japanese characters is displayed as dots.
8. Delete the style by clicking the trash icon on the right top corner.
9. Close the Template style list.
10. Reopen the Template style list.
11. The style with Japanese characters is then displayed correctly.

Also, when styles named in Japanese and styles named in English are mixed in a list, the issue can occur or resolve depending on the order.

You may want to try reordering the styles as a temporary solution.

I understand that this behavior is not ideal, and I will create a report for our product team to track this issue. While we cannot guarantee when or if this behavior will be changed, we sincerely appreciate you bringing it to our attention.

Thanks for your help!