Anyone know where I can get a Statutory Declaration witnessed in Khon Kaen?

The document only requires someone to witness who, and I quote

" Any person having authority to administer an oath in that place" with the place being Thailand

Just go to any lawyer office and ask them if they van notarize it for you.

Any Thai lawyer should qualify, provided they have their special lawyer ID card, which you should get a photocopy of just incase. As when I first did this for a document with my lawyers in NZ, I think they had to trace his registration or something to ensure he was legit, but thereafter, it was easy as (I assume they checked his details, as on the next one they asked me to use the same guy if possible, as it'd make it easier for them).

But also check what the document is related to when you make your statutory declaration, as there are some which might require your embassy's staff to witness (e.g. For my affirmation to marry, I had to make a statutory declaration at the NZ embassy saying I was legally able to marry, and I believe that this did indeed need to be done there, not just at a lawyer's).