OK. The fact that you see English text in the footer means that you have not customized the theme...
* Go to uStore admin
* Select the store
* From the store setup button, select customize theme
* Click footer setup
* Delete the English text and type in Thai text for the headings and text fields.
* When done, click the publish button.
After this process, both English and Thai localization should show Thai in the footer.
This is the way the "customize theme" editor is designed - it does not give an option to edit the theme for different languages.
If you have the ability to create a custom theme, then you can add a localization file in the theme and publish a new theme using these instructions:
To add a localiztion file:
* Duplicate /src/localizations/en-US.json file and name it by the localization you need.
* Edit the file and change the texts
* Edit the index.js file in the same folder and add the new localization in two locations - in the import and localizations const.
* run the install and publish scripts as described in the wiki documentation.