Do I need to exit Thailand to renew my student visa each year?

You misunderstand how the ED process for a degree program at a uni here works

You get the initial 90 day Non-ED visa, (either before you come here via a thai consulate in your country with documentation from the uni, or after you're here at the immigration office, again with documentation from the uni)

Then when that 90 days runs down you get more documentation from the uni, go to the immigration office and apply for an extension of stay for 1900baht.. Most degree programs get extensions a year at a time.

When your year runs out you get paperwork from the uni and go apply for another yearly extension.

You do this the whole time you're enrolled in your degree program.