Fish from Thailand...

[Vie]

Anyone know what this is

Photo was taken at Sak island (Ko Sak), Pattaya area (north eastern part of the Gulf of Siam, Thailand) in sandy area/shallow water (6-8 msw).

Fish appears to be very small (see urchin spines for scale).

 

[smellzlikefish]

Looks like a type of pearlfish. Great pic! Many species of pearlfish (aka assfish) live in the rectums of sea cucumbers and sea stars and parasitizing the gonads of their host. Not sure of the species.

 

[Quero]

Pearlfish was my first thought as well. Some pearlfish are parasitic, and some are simply commensal. There is a third type that swims freely.
This one looks like it might be Encheliophis homei. More info on FishBase.

 

[Vie]

I'm still not quite sure what it is, it reminds me of certain knifefish species (but they are freshwater fish from S. America). I was under the impression that pearlfish are mostly nocturnal and have somewhat translucent bodies.

 

[smellzlikefish]

Vie-Soe pearlfish are transparent but not all. You are correct in that knifefish (order Gymnotiformes) are freshwater and don't have any saltwater near-relatives. I'm sticking with free-swimming pearlfish.

 

[ryan115]

I believe pearlfish tend to have a continuous anal fin down the length of the body. The fish in the picture has an anal fin that begins mid body. You can also distinctly see the pelvic fins on this fish.
I am leaning towards a member of the family Ptereleotridae, Dartfishes
Fish Identification

 

[Quero]

I thought of dartfish, too, as I know I've seen some long, pale ones slip back into their tunnels, but I can't find a specimen that looks like what I think I've seen in the books. They always move so fast that I've never noticed the fin placement.