i' m looking at moving to thailand permanently.

i'm married to a Thai and I'm an Australian citizen,what type of visa is required and do I need to leave Thailand periodically to

renew my visa?

There is no specific visa required but being married allows a non immigrant O visa. If using visa entry each stay can be up to 90 days. With 40k monthly income or 400k in Thai bank account two months one year extensions of stay are available from Immigration inside Thailand and can be done yearly so no exit required.

Yup, plus if over 50 a Retirement Visa is also available, higher financial requirements but usually easier to extend.