That sentence doesn't really make sense to me.

Do you mean that you want to populate tags for a thread if there are no tags already and someone responds to the thread? If so, this may be possible.

Perfect

Installed !

I mean
The amendment that I have done only for new post
But old post does not add topics
Can I make my words appear in new reply

Yeah, I like that idea too.

I'll have to check to see whether I know about the thread at this point and whether updating the post will affect the thread... it may not.

<font color="Lime">*Installed*</font>

What's the possibility of making automatic tags for threads that already exist?

This would really be good if it did it for older post too. Is there a way to make it add tags weither or not tags are added?

What are you looking for?
1) Incrementally fixing old threads by populating tags if those threads are replied to?
or
2) Generating tags for all threads that have none?

To be honest I don't think doing all non-tagged threads would be difficult... the code is already up there and I'd just have to iterate over all threads.

Yes, certainly ...