is it possible if i make lets say, change all the scottish leagues into 'thai' leagues, and also by all the scottish teams with thai teams?
without changing the number of teams.

could you explain it in a bit more detail please?

Yes, absolutely. Here's a thread in which the OP does a similar thing, so he's bound to know how to, as would a lot of people in the Editor's Hideaway.

He means to switch the Scottish teams with Thai teams and turn the Scottish leagues into Thai.

And, you can't change the amount of teams in a league, if you do that nation becomes unplayable. Just click on a Scottish team on the Scottish League page, click switch and then whichever team you want. This should be in the editors, I think.