One of my best male buddies is basically a early 20’s guy, even though he is currently in his 70’s. He has always been that way and appears adjusted at least outwardly.
No kids, never married, single, still drinking rum & cokes. His primary social circle is guys in their 20’s-30’s. He has no desire (or need) to grow up and act mature. Some guys are just like that. I think Thailand attracts these kinds of guys.
If you were to argue a point with him about not growing up you would lose every time. The only “tell” is when he is sitting there by the pool or in a bar with a bunch of younger guys and how weird it looks, although he would never see it.