The judge at Phnom Penh Municipal Court handed Ratree a six-year jail term.
The charges carried a maximum combined sentence of 11 years and six months.
Veera, dressed in a blue prison uniform, denied being on Cambodian soil when he was arrested.
"I was walking on Thai territory," he told the court through a translator. "I had no intention to invade Cambodian territory."
Veera and Ratree were also fined 1.8 million riel ($445) and 1.2 million ($300) riel respectively.
The pair were among seven Thais arrested in Cambodia on December 29 while they were inspecting disputed border territory.
The neighbouring countries, long at odds over their border, have both stressed they want to avoid a row over the issue, although Cambodia rebuffed Thailand's initial demand for the detainees' immediate release.
The Thailand-Cambodia border has never been fully demarcated, partly because it is littered with landmines left over from decades of war in Cambodia.
Around 2,000 nationalist Thai "Yellow Shirts" rallied in Bangkok last week to demonstrate against the government's handling of the border dispute with its neighbour.
The Yellows, who claim allegiance to the throne, are powerful players in Thailand's colour-coded politics.
Officially known as the People's Alliance for Democracy, they seized two Bangkok airports in late 2008, leaving more than 300,000 travellers stranded.
They used to be closely linked to Thai premier Abhisit Vejjajiva but relations have since soured.
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