You can't. Unless the you and OP both PM theymos with an agreement, there is pretty much a zero percent chance that said thread will get transferred. I don't think (or at least remember) any exceptions done by theymos although you're free to search around or just PM theymos.
I cannot lock or change that inital thread. I can control only the thread about DMD Diamond which we have created after this coin takeover.
This initial abandoned thread s been created by the old dev who s not around for years.
Did you try to report it to be moved to archival?
There's no need to report. Anyone can move their thread to archival (and have no right to move them to its child board though).
BTW can you post the link to the thread? This could help.
Read what he's saying. He didn't create the thread; an old dev did so that's why he can't do anything about it. I would contact an admin as they can transfer ownership, merge or decide what to do with it but it wont be deleted. Best likely option would be a merge of the two threads and transfer ownership over to you but you'd have to make your case to an admin for that to happen.
Merging rarely happens as the feature was coded in as an addon and as such is rather clunky and messy in SMF.