Here, we live close to the border of 2 other states (WI and IA) which both have different tax rates. For vehicle purchases, if I go to WI I have to still pay MN taxes on my vehicle because I am a MN resident - it is the law. If I make "regular" purchase like clothing or food or small appliances, I only have to pay the taxes to the state I made the purchase in regardless of the state I live in. There is a little known "rule" that if you spend more than so much in another state accumulating "small purchases" you are supposed to report the tax difference, but who the heck does that :)
I would call a dealership in OK and ask them directly if you have to pay TX taxes if you are a TX resident. They will give you the straight "poop." Oh, here we have to have and show a DL to buy a car so you cannot "fib" and say you are from a different state. Probably the same there, too.
Good luck!