The Cambodian court's sentencing of yellow-shirt activist Veera Somkwamkid and his secretary Ratree Pipatanapaiboon to jail was unfair, Democrat Party MP Panich Vikitsreth said on Wednesday.
Mr Panich, one of the seven Thais who were arrested by Cambodian soldiers on Dec 29 for illegal entry, said he felt for Mr Panich and Ms Ratree and was very disappointed with the verdict.
He said the additional charge of espionage against them was unjustified because they had no intention to steal anything from Cambodia.
"Mr Veera initially thought that the pinhole camera could not capture pictures, while Ms Ratree was only taking photos as souvenirs.
"I'll do my best to prove all seven Thais are innocent by working with the government to present the truth," the MP for Bangkok said.
Appeals would filed as soon as possible and all charges would be denied, he added.
Mr Panich used the Thai phrase กล้องรูเข็ม (klong ru khem, or needle hole) for pinhole camera, but gave no other explanation.