Different batches of Thai stick doesn't prove anything. You seem to be basing your entire belief on the hearsay of a friends uncle? You've already stated you weren't there. People tell all sorts of stories, especially if there is money involved, and an illegal product.Thai sticks being imported in to here the US and other places were not all from the same batch you had distinctly different Thai sticks so they were from different Thai sativa lines.
Opiumated Thai sticks were not common they would pop up here n there and when they were available you still had normal Thai sticks to pick from.
If you look at the old photos that have been posted even in icmag alone of Thai sticks you will find many different looking Thai sticks .
It's not something that can ever be proved either way. To me the whole thing makes no sense whatsoever, apart from the point of view of marketing a product.
There's also no evidence from authorities in Thailand, USA or Australia that I'm aware of, despite the fact that drug seizures were analysed. If there had been opium added to Thai stick I think that info would be out there, outside of stoner circles.
The best quote in the whole thread is from Sam S on the first page;
"I agree I never saw Thai sticks in Thailand with Heroin wash or Opium added it is just made up to help sell the sticks. Opium is much more expensive that Thai sticks were why would Thais want to do this? I knew many in the trade in Thailand none thought it was real, all thought it was made up, also the best Thai did not need anything added. I visited Thailand a dozen times over many years and my focus was always Cannabis or Cannabis seeds." -SamS