Updated

A preliminary autopsy shows liver cancer killed a Thai prisoner who was serving a 20-year term for sending insulting text messages about Thailand's royal family.

An observer at Wednesday's autopsy said Amphon Tangnoppakul had late-stage liver cancer that likely developed after his 2010 conviction. Cherdchai Tontisirin said there were no signs of physical abuse.

The case of 62-year-old Amphon drew attention to Thailand's severe lese majeste laws. Known as "Uncle SMS," he had denied his guilt and testified he didn't know how to send text messages.

He lawyer had said Amphon died Tuesday, a few days after complaining of stomach pains. He also had mouth cancer.