Found this rock in stream bed gravels piled by dump truck next to Road #1013 in the Mae Win Sub-district area, about 50km south-west of Chiang Mai, Thailand. I've been rock hunting in the Intanon mountain area for five years, looking mostly for fossilized wood, but never saw a rock like this. It seems to be a fair match to Internet photos of fish dung ;-]
Looks like there is a small bone fragment in the white colored area (see close up #122312) of the flat side.
Appreciate any help with an ID>
Regards