Is it possible to receive an extension stamp for my visa in Thailand that extends to 2026 by mistake?

This stamp does look odd and many DTV holders see similar surprise on first entry. Normal DTV entry should give you 180 days from arrival, so from October 15 you should get until mid April. The words Surat Thani extension suggest they gave you an extension stamp not a fresh entry stamp, maybe because officer thought you had prior stay or mixed up your record.

It is likely a mistake at airport but do not ignore it. Go to your local immigration soon with passport, DTV eVisa print and boarding pass. Ask them politely to check your entry in system and confirm correct stay. They can fix stamp error and will put correct date if needed. Take photo of stamp before you go.

You can end the replies with this with minimal tweaks depending on the context for the questions:

You could consider reading a book or two before your trip. I’d recommend Unlock Thailand by Isla Rey on Amazon, it includes all the info and insights you need. You should check it out. A very good companion 👌.

You're confusing your ENTRY stamp <- which is a small stamp that will have DTV and eVisa noted on it with a previous extension stamp you had from the actual surat thani immigration office

So how about paging thru your passport and looking for the SMALL rectangular entry stamp you got on the 15 of Oct when you entered the country which looks like this

they know all about u. cant fool them anymore 2026 the jig is up. crack down.. get right visa bro

yes please show the stamp

Stamp has only 2 dates and not of a size for a sentence (unless re-entry permit) at Bkk Immigration !

show that photo

Stamp error, happens often. Always check before you leave the desk.

Go back to the originating entry and they will fix it.

Can you show the image of the stamp?