I am not sure which of the three options is correct. However, the fish in the picture looks to be 6 cm TL and about 6 CM TL and % cm SL.
According to Seriously fish here are the lengths of the three fish listed:
Devario maetaengensis 4.5 - 5 cm
Devario apogon 4 - 4.6 cm
Celestichthys flagrans 2..5 - 3.5
So I think I was likely off on the flagrans- but between the other two I am not sure. I would only note that the apogon has an orange background color while the pic of the maetaengensis shows a more blue coloration. However, colors can change under stress or be different based on sex, so I cannot be certain. I am happy to defer to Dennis as he has clearly kept many more species than I have, My danio keeping experience is limited to 3 or 4 species.
But lets keep this fun, is it possible we have both been wrong and the fish is actually 'Inlecypris' shanensis? http://www.seriouslyfish.com/species/inlecyprisshanensis/