If you're creating work set within the Cthulhu mythos of H.P. Lovecraft and his kindred writers, and using Laos as a setting there are a number of existing entities who are rift with possibility for incorporation in part or at the heart of a particular story, image or poem. We've discussed the possibilities for Nyarlathotep, for example.
Among those who I would prioritize for consideration in a story set in Laos include:
Serpent People.Created by Robert E. Howard, they first appeared in "The Shadow Kingdom," published in the August, 1929 issue of Weird Tales. The authors Lin Carter and Clark Ashton Smith included them more fully in the Cthulhu Mythos, taking a cue from a note in Lovecraft's "The Nameless City." There, an Arabian city had been built by a pre-human reptilian race. "The Haunter of the Dark" features a more explicit mention of the "serpent men of Valusia" as being one-time possessors of the Shining Trapezohedron, according to Lovecraft. Because of Lao legends regarding relationships to the Nak, there are some interesting possibilities to consider.
Tcho-Tcho.August Derleth created the Tcho-Tcho tribe in "The Thing That Walked On The Wind." An Asiatic race occasionally considered sub-human, the Tcho-Tcho are polytheistic, most commonly known to worship, Chaugnar Faugn and Hastur. They are often connected to the mythical Plateau of Leng but their range is believed to be throughout much of Asia.
The Father of Serpents established by H.P. Lovecraft in "The Curse of Yig," is primarily connected to the Americas, but there is nothing to suggest that "the half-human father of serpents" could not have influence elsewhere, particularly in Southeast Asia where there are an abundance of snakes and snake-like creatures constantly being discovered.
Created by Frank Belknap Long in "The Horror on the Hills," Chaugnar Faugn is found in a cave in an Asian mountain range. Worshipped by a branch of the Tcho-Tcho, it has a vaguely elephantine appearance, almost like Ganesha. However its trunk terminated in a large floating disk that drains blood from its victims. It's normally encountered as a grotesque statue but may stir at night. Considering Laos was regarded as the Realm of a Million Elephants, dealing with a statue of Chaugnar Faugn or Chaugnar Faugn itself is reasonably plausible.
"The great water-lizard" mentioned in H.P. Lovecraft's "The Doom That Came To Sarnath." It's considered greenish blue and iguana-like, almost twelve feet long but found primarily in the Dreamlands. Could it have connections to the Nak or Zaj of Laos? It could be worth exploring for an intrepid writer.
Laos is a landlocked country but the myths of Phra Lak Phra Lam and others allow for legends of islands like Lanka, and presumably an island like R'Lyeh or Mu, the home to Lovecraft's creation, Ghatanothoa, found in the story "Out of the Eons." It possesses myriad tentacles, maws and sensory organs. Rumored to be found between New Zealand and Chile in the Pacific Ocean, this would be an interesting being in relation to the other water-dwelling entities of Lao myth.
Created by August Derleth in "The Lair of the Star Spawn," Zhar is said to dwell in a dead city buried beneath the Plateau of Sung or Tsang in China. It is known as the Twin Obscenity, but it is possible it may live in other locales. The similarity to the Hmong word Zaj, or dragon/naga, etc. may well be worth exploring.
But which entities do you think would work well to connect Laos with the Cthulhu Mythos?