Is there a state labor law that says how much notice a non-hourly employee must give when leaving position? i.e. two weeks, 30 days? I understand it is courtesy to give 2 weeks but is it law? thanks

No, there is no law specifying the amount of notice an employee must give. Two weeks is the customary amount.

No, it is not law. There is no law in any state, including Texas, that dictates how much notice an employee must give, and no law in any state, including Texas, that dictates how much notice an employeR must give except in situations that would trigger WARN or a state equivalent.

Nor is there any such Federal law (again, other than WARN).