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I will guess that these are Gesomyrmex luzonensis.  The key in Dlussky, Wappler, and Wedmann, "Fossil ants of the genus Gesomyrmex Mayr (Hymenoptera, Formicidae) from the Eocene of Europe and remarks on the evolution of arboreal ant communities" (Zootaxa 2031: 1–20 (2009) is for gynes only, but I'm extrapolating a little.  Also, I suspect there are more than the six named extant species.  Arboreal ants, especially in places like Southeast Asia, have not been exhaustively surveyed.

The species guess would be aided if we knew where these ants are from.  Gesomyrmex luzonensis is from the Philippines. 

Extract from Dlussky et al:
Only three direct observations on living Gesomyrmex are published. Wheeler (1930) cited a letter from
Dr. James W. Chapman, who observed and collected a colony of G. luzonensis near Dumaguete, Philippines.
During three days Dr. Chapman observed foraging minor workers, which were attracted by ripe bananas. He
noticed a peculiar jerky, zigzag gait of these ants. During the day several workers were seen to visit and feed
on the bananas. The last one retired to the nest at 5 pm, apparently for the night. The nest was in a pole, which
Dr. Chapman cut about two weeks previously and placed diagonally between two of the posts, to serve as a
brace. On the third day Dr. Chapman opened the nest and found that “the four entrances were seen to unite to
form a single funnel-like passage, which grew narrower towards the end of the pole and opened into the
middle of the main nest-cavity. This was about five inches long and one and a quarter inches from the surface.
The two ends of the cavity were rounded out and the wood around the excavated pithy centre had been
gnawed away to form several irregular galleries. The colony had evidently been nesting in these cavities for
some time. There were about 150 adult workers, their queen, male and a number of eggs and larvae”.
The second observation was published by Cole (1949) who described G. spatulatus from a series of 25
workers collected at Jorhat, Upper Assam, India. He wrote: “The ants were running up and down on the trunk
of a tall tree located in a sunny area beside a rice paddy. They were very agile and ran swiftly with a jerky
motion. There was indication that the nest was arboreal, although there was no actual evidence to substantiate
this view”.
More recently De Greef (2007, p. 11) reported on a colony of Gesomyrmex (possibly G. tobiasi) in the
Virachey National Park, Cambodia. “Some workers were initially found foraging around the camp area, and
were baited with live termites and mosquitoes. After a few hours the nest was found inside a branch of 5 cm
diameter, the entrance being a tiny hole of 1 mm diameter. The branch was cut open, delivering dozens of
workers of very different sizes, along with larvae and nymphs. Another colony was located nearby and left
undisturbed, for further study on their behaviour”. Considering this, it is clear that Gesomyrmex is arboreal,
inhabiting the lower vegetation or the canopy.

If the person who took the photo was able to observe and record any of the behavior of the ants, the information might be useful.

H