I think I know what the problem is. I’ll fix it next week.
Your site’s default locale is set to “English (United States)” and you have customized text content.
In the meantime please make sure that you override the oneandother keys or remove the override of the other key.
On your screenshot it doesn’t look like there’s a translation override. I guess you switched the locale in your user profile to something other than “English (United States)”. Customize → Text Content always uses your language, not the default locale. You need to set it to “English (United States)” before you see the translation overrides that your forum uses.
Out of curiosity: Why are you using English as default locale and override some texts with localized content? Why not simply use Thai and customize those texts and contribute missing translations on Transifex?
Old time I start use discourse by not know anything. I don know is has thai. I know is we can edit context from en to th yes i use it 30%
Until I knew that there was a way to translate this with Transifex later But now my website is focused on producing content for visitors. So there was not much time to come with the translation