Former foreign minister Kasit Piromya insisted his administration did its best to help secure the release of two Thai Patriots Network activists from Prey Sar prison in Phnom Penh.
Mr Kasit was responding to activist Ratree Pipattanapaiboon's claims before the Senate committee on human rights, liberty and consumer protection last Thursday that the previous Democrat government failed to offer proper assistance for securing her release.
Ms Ratree had also criticised the Democrats for failing to counter Cambodian accusations that she was a spy.
Ms Ratree was released from the prison on Feb 1 after receiving a royal pardon on the occasion of the funeral ceremony of Cambodia's former king Sihanouk.
Ms Ratree was arrested along with Veera Somkwamkid and five other Thais by Cambodian officials on Dec 29, 2010, while inspecting land disputed by the two countries near Ban Nong Chan village of Sa Kaeo' s Khok Sung district.
Veera and Ms Ratree were later sentenced to eight years and six years in jail, respectively, for illegally entering Cambodia and spying. The others were released earlier because they admitted to the charges.
Cambodia's Ministry of Justice has reduced Veera's jail term by six months.
Mr Kasit said the previous Democrat-led administration had instructed several security agencies to help Ms Ratree and Veera to the best of their abilities after the two were charged. Two lawyers were provided to help them fight their cases.
Mr Kasit said the foreign ministry helped their relatives visit them in jail.
He also rejected claims that former deputy prime minister Suthep Thaugsuban _ who was assigned to hold talks with his Cambodian counterpart Sok An on the disputed 4.6 sq km area near Preah Vihear temple and the disputed maritime zone in the Gulf of Thailand _ reaped personal benefits from the discussions.
He said the talks took place in Hong Kong but they were held in a transparent manner.
Cambodian authorities claimed in 2011 that Mr Suthep held secret talks with them about overlapping oil and gas interests.
Mr Kasit said the government should negotiate with Cambodian prime minister Hun Sen to solve border problems.