"Took this photo in a cave near Krabi, Thailand, and figure it is a Hornbill sp.?"
Hi Hanno, is it the bill shape that you base your guess on, or is there something else.
Further to the above, a little research shows only 13 species of Hornbill recorded in Thailand. The bill edge serrations in the picture seem to be slightly overdone, but apart from that, it would seem to be a Hornbill. Out of the 13, going by the drawing, only 2 would seem to fit the drawing outline, the Great Hornbill, Buceros bicornis, or the Oriental Pied Hornbill, Anthracoceros albirostris. Your guess is as good as mine, but at present the status of both is, the former, "vulernable" and the latter "common". Depending when the drawing was done, it could be either.
I will guess at the Oriental Pied. Why not. It's only a guess.
Regards
Malky.