Residents of Nanonbong in the northeastern province of Loei have waged a decade-long struggle against the mine, operated by the Thai company Tungkum Ltd, which they say pollutes the environment and damages health.
The company has responded by filing at least 19 lawsuits against them, according to rights groups, including charges of criminal defamation against a 15-year-old girl.
In May 2014, a week before the coup that brought the current military regime to power, Nanonbong villagers said they were mobbed and beaten by over 100 armed men while they were blocking the road to the mine.
The pair was also ordered to pay compensation to some of the victims.
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"In the verdict, the judge mentioned that the two suspects hurt villagers to clear the way for transporting minerals," lawyer Sor Rattanamanee Polkla told AFP.
"I hope that this verdict will make authorities more careful in the future," she added.
The ruling is a rare departure from the impunity often granted to soldiers in a country where the military routinely intervenes in local and national politics.
"We are disappointed that only two people were indicted and found guilty," she told AFP.
She said over 100 community members gathered peacefully outside the courthouse this morning and handed out flower chains to police officers.
"It was quite an extraordinary gesture," she added.
Earlier this month, the Thai government announced it would shut down gold mining across the country, an unexpected move in a country where profit often takes precedence. The current regime has pushed through a string of controversial environmental projects.