I know Jason Momoa mostly from watching Stargate Atlantis. I haven't even seen Aquaman yet. I looked it up and an article said he learned slide guitar while on the set of Atlantis. During Aquaman he learned bass so he could jam with one of his co-stars. Although the article didn't go into much detail, it seemed to indicate he is having a good time adding basses to his collection. Aquaman was shot in 2017. So I imagine since that time he has had the time and money to do what he wants, including apparently buying some nice guitars and basses. From what he was saying on that video, it seems that Thunderbird was a gift, though.