This may have been one of the smallest animals that I photographed in Thailand, but it had the best name — the orange bellied flowerpecker. A lovely little bird of equal parts orange and blue. This is the male of the species. The female is more uniformly yellow with a bit of black.
Nikon D500 with Nikkor 200-400mm lens (at 400mm) ISO 800, f/4 at 1/160th of a second