Because I've gotten salty about Bedtime Stories paraphrasing all the cool stories but not crediting authors in multiple cases:
For the first video:
The Da Nang flying humanoid story may hail from any of these mentioned:
https://mysteriousuniverse.org/2015/10/the-glowing-winged-woman-of-vietnam/
or something in the source section of the flying humanoids article in Mysterious Creatures: A Guide to Cryptozoology, by George M. Eberhart (p.177)
The Ahool is a giant Javanese cryptid bat that is soley described as a bat, attested by European researcher Ernest Bartels and only by he (can't find a source though). Name onomatopoeic. Can't say it has much to do with the flying humanoids in Mexican videos and is not siren-like.
The giant gold fish should probably be credited to
Very Crazy, G.I.: Strange But True Stories of the Vietnam War (2001) by Kregg P. Jorgenson.
The Vietnam giant snake /only/ turns up results of the photo that this video attributes to Remy Van Lierde. Not many, too.
The only sourced instance of the lizardmen story i can find points back to
https://web.archive.org/web/2017071...nam-recent-wartime-reptilian-cave-encounters/
from 2017, with some more recent hits for the images that it comes with on a Bulgarian media site. The Mysterious Earth author's articles include Annunaki material and content about the presence of aliens at Jesus' crucifixion. The story is attributed to an anonymous submission, so this might be its first place online. The "newer" sighting with photo may similarly be from here, since I'm not finding older examples.
(I like treasure hunts, so if anyone has sources/old instances of anything I'd love those. ....I don't actually care whether I find an intentionally fictional story, an account purporting by all context to be real, or something that I can't actually source at all. I just like the hunt. this has been fun. Also people should credit their sources.)