Can I leave Thailand and re-enter before my Non-O extension appointment?

I will be applying for another extension of stay Non-O based on marriage on Monday, July 22nd at Chaengwattana. My current extension expires on August 29th. I know that I will have to be back around 30 days later to receive the approval and passport stamps. My question is will I be able to leave the country and re-enter before the appointment date? Will I need to get any type of re-entry permit after I apply or will I just be able to come and go on my current multiple entry before it expires/ appointment date for new extension whichever is first?

Thank you.