Can I mail my 90 Days Report to Bangkok immigration 24 days before the due date?

Where to mail it? Is it E-mail mailing to immigration in Thailand?

My experience, I always mail mine in 2 weeks in advance, I use EMS both to send & receive. Cost about 100b

Good luck

For Bangkok:

I sent one for my daughter 23 days before the due date and the slip came back without any note that it's too early. Last time when the online system didn't work (showing overstay in their system = not updated), I mailed it on -15 with a note explaining the situation. And the slip was sent back with a note saying something like don't be late next time (no fine).

At this moment, I'm still waiting for the slip I mailed on June 14th which is -22 days, delivered to the immigration on -20, the documents I sent wasn't returned telling me it's too early. So I presume they are processing it.

That's my experience, and there's no guarantee it won't get rejected but hope this helps.

Never forget Thai immigration is up there with German bureaucracy when it comes to being anal. The letter you mail in "should" be postmarked 15 days out. I'm not saying it won't work, but personally I wouldn't risk it, because if whoever opens it sees that it's more than 15 days before the due date, it will most probably be returned to you as being outside the window. Why not just get it all ready, and pin it to your front door with a note saying "post on xx date" to remind you?

Maybe just write "don't open until (whatever date is 15 days before your 90)"

Like a fun Christmas or birthday surprise, lol

shouldn't be a problem but I dunno really. No one ever wanted to mail one in that early. All you can do is try it and see if it works.