I recommend Elephant Nature Park (there's also another one with waterfalls in their area I just forgot the name). They have a limit on the # of volunteers and only the mahout can ride them. They have a special relationship with their mahouts so they're okay if a mahout rides them but not just anyone, their backs are not (anatomically) designed for riding.
It's good that you've mentioned some bad things they do there to the elephants so travelers would be aware. Thanks!
Thanks for commenting! It’s a good thing that they restrict the number of visitors so that the animals are not totally stressed out all day. Thanks for the tip about the other park, gonna see if I can find something about it on the internet.