Compact Coral (Diploastrea-heliopara)
Observed: Koh Chang Reefs, 2015
Observed By: Jonathan Milnes
It seems that corals have all kinds of vernacular names. This one is know as Compact Coral, Honeycomb Coral and Diploastrea Brain Coral. Pick one you like and go with it.
It is an intricately patterned hard coral that is widespread throughout tropical waters all across the Indo-West Pacific, including the Gulf of Thailand.