Topic: Transfer from old to new passport + 90 days

Good evening ladies and gents,

* I recently (Friday 8 March) transferred my visa extension from my old passport to my new passport at Chaengwattana Immigration.

* I got told to head to my local immigration in April with the TM47 document to renew my 90 days.

*My days 90 expires on 16 April.

My eventual problem:

* I am flying out on Sun 7 April and returning to Thailand on Fri 19 April.

My questions:

* Do I need to head to my local immigration before flying?

* What is the correct procedure to do this?

* How to avoid penalties?

I know it is maximum 14 days prior or 7 days after due date but feel like this process might be slightly different from what I am used to. I feel like I might have to go twice. Once before flying, and once after flying. Or is this not necessary? I don't wanna end up paying a 2k fine.

Thank you in advance for your wise and helpful comments!