im practicing some pentatonic scales and i was wondering if i should be moving my thumb to differnt positions while playing or if its ok/better to keep it steady? i can play smooth and somewhat fast and i keep my thumb steady against the back. i do this so i can get better at hitting the strings with the tips of my fingers and have more finger control but i dont want any bad habits forming. thanks
i think the correct way of doing it is to keep your thumb centered at the back of the neck
"every prince has to slay a few dragons before he meets his princess"
in my opinion, yes the thumb should be moving when you're going up and down the neck.

i think the general guideline you should follow is: don't have your thumb gripping the neck too tightly and don't use excessive strength to fret notes. everytime you practise scales, make it an effort to use the least strength possible. this will allow you to play fast and fluidly.

you know that you're doing all i've said above correctly, if your thumb is able to move up and down the scale.
Is thumb centered at the back of the neck the standard way?
I found that if I play high notes, especially the high E string, I tend to put the thumb around the neck..

But when I look at Paul Gilbert playing, he does that too..
i think that will depend on your personal preference?

but my opinion (as well) is that: your thumb should be resting at the centre of the back of the neck as much as possible. i think you should try to avoid gripping the neck like a baseball bat as in the future, you might find that it'll hinder your ability to play certain progressions.