The photos taken during the Tsunami were done for ID purposes. The bodies were in incredibly bad shape and photos were taken to preserve what was left of them. This includes photos of any remaining characteristics such as tattoos, jewelry, deformaties, and anything else that could be used to potentially ID the bodies later on.
After the photos were taken, the bodies were buried along with numbers so if they were identified later, they could be dug up and given a proper cremation (this is Thailand). The photos taken of the corpses were posted publically in the hope that family members could possibly identify the corpses to find their loved ones.
There is nothing 'sick' about it.
The original intent of the photos is one thing, you passing them around the internet is quite another. Do you deny offering to show them to me, or that you've shown them to other freepers?