Rahu

Churning of the Sea of Milk
South wing of east gallery
Angkor Wat

The first of three large devas on the north side of the relief (diagram, #5) is probably an asura in disguise. For example, the top of his headdress is like the asuras' and different from the devas'¹. Rahu seems to be a likely candidate for this figure², due to his importance in the Churning myth. Rahu disguised himself to infiltrate the gods' encampment. After the churning, the gods got hold of the elixir and did not want to share it with the asuras. When Rahu tried to abscond with it, Vishnu decapitated him as punishment. Rahu's bodiless head continues to hurtle through the heavens, periodically causing eclipses by devouring the Sun and Moon, which, however, soon pass through his bodiless mouth and out into the sky again.

The 88 gods on this side of the relief correspond, according to Mannikka, to the number of days between the spring equinox and the summer solstice³.

Notes:
(1) Some authors reinforce the case for this figure being an asura by alleging that its mouth has fangs (Mannikka p.164, Roveda p.50). No such dentition was visible when I saw the carving (February 2004, photograph above).
(2) According to Roveda (p.49), Coedes thought the figure might be either Rahu or Shiva.
(3) Mannikka counts Indra (diagram, #4) as an 89th deva to make this calculation come out.