Can I Leave Thailand Before My Immigration Follow-Up Appointment?

1 question that I'm not sure has addressed; I paid the 1900baht for a 30 day emergency extension. I received the stamp that many of you have probably also recieved: "The application of stay is under consideration; applicant must contact again in person", along with a stamped date in which to return (in my case April 8). You must return to the same immigration office, & I happened to apply in Isan Province- some 8 hours from Bkk. I have since returned to Bkk. But my question is- it looks like I may be able to fly out of here sooner than expected. So I were to leave before returning to the immigration office, where would my passport stand & would I be allowed to leave Thailand? As I say the follow up date is April 8, & my previous visa extension ends on April 3. Is that April 8 the current alloted time I would have? Or do I need to return for the follow up to get stamped for the remaining time? Thanks