The local telecoms employee died in hospital after the elephant gored his chest with its tusk as he ate hotpot with a fellow worker in the coastal city of Rayong late Monday.
"They were talking to the mahout (elephant keeper) about buying food for the elephant when it suddenly stabbed one man in the chest with its tusk and kicked the other," local police Lieutenant Thawat Nongsingha told AFP.
The mahout has been charged with offences including violating animal welfare legislation and negligence causing death, Thawat said.
The maximum penalty for negligence causing death is 10 years in jail and a fine of 20,000 baht ($600).
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Thailand's roughly 4,000 domesticated elephants outnumber an estimated 2,500 remaining in the wild. The capture of wild elephants for entertainment use is banned.
Domestic elephants in Thailand -- where the pachyderm is a national symbol -- have been used en masse in the tourist trade since they found themselves unemployed in 1989 when logging was banned.
They are prohibited from entering cities but incidents of mahouts using the animals as a tool for begging are not uncommon, while elephants are frequently used legally for the amusement of holidaymakers in camps and zoos.