Not update again
Several months ago I asked you why an old message still appeared in Wikipedia although it was updated. The issue was resolved. However, today I found a similar problem again. This link shows that two messages relating to RecentChanges page were updated two days ago. Yet, only one appears correctly in the RecentChanges page in Thai Wikipedia, while the other one was not updated.
More interestingly, I opened RecentChanges page in translatewiki.net and found that neither of them was updated. This is strange because translatewiki.net should update its interface immediately after changing of any message. I, therefore, did null edit on both pages and found that RecentChanges page on translatewiki.net now renders correctly. RecentChanges page in Thai Wikipedia does still render incorrectly, though.
Are you sure that recentchanges-legend-newpage hasn't changed in English too? LocalisationUpdate only updates translations if the English text is still the same as the one used by the wiki, you may need to wait a week or so for MediaWiki to be updated there.
You need to check how it is in 1.23wmf6 on git.wikimedia.org
Well, I still don't understand what happened.
This link at line 678 retrieves the message named "recentchanges-legend-newpage." This message is defined in this link at line 1569 correctly. However, in wikipedia:th:Special:Recentchanges the recent version of "recentchanges-legend-newpage" still appears which is completely incorrect. It has been like this for almost one month.
Now the wiki uses the new message in English  so it's definitely a bug: please report it in bugzilla against the LocalisationUpdate extension (and cc me), these links are enough to prove the issue.