There was a small Village on Road 2375, about 1km back, so I walked the bike back there. I moved slowly through the Village, looking for a place that might be in the tyre business, with a dozen dogs venting their annoyance at the stranger in their midst as I went.
Soon enough I found a small shop that clearly specialised in fixing motorcycle punctures. I called out, into the empty shop, and soon a middle aged, friendly-faced bloke came out. I explained, by sign language, my problem. His initial reaction was that he had a replacement 26inch tube, but it was too narrow, but I said it will work fine!
He helped me fit the new tube, and blow it up...he was interested in my quick release axle, as he had evidently not seen one before.
Cost 60baht...about AU$2.50...I gave him 100 baht, and he was delighted!