Is it essential to go to Chaengwattana on the exact date for my non-O Thai wife's year extension stamp?

Chaengwattana has a ZERO tolerance policy on you showing up late for that under consideration stamp close out on a marriage extension.

Your paperwork is setting in Section L-2 on the day you're supposed to show up. I have seen someone who showed up a few days after that date get his extension denied and have to start the whole process all over.

Go late at your own risk

You MUST return on July 21, unless there's a very good reason