Senator Somchai Sawaengkarn plans to use a general debate to grill the government on reports of Thaksin Shinawatra's planned visit to Myanmar and the administration's failure to bring the fugitive ex-premier back to the country.
The Senate is looking to invoke Section 161 of the constitution, which will allow for a general debate to be held in parliament without requiring a vote.
The Senate has asked the government to schedule a date for the debate, which was originally intended to focus on the controversial rice pledging scheme.
However, after reports of Thaksin's visit to Myanmar emerged, accompanied by a lack of urgency on the part of the government to seek his extradition, the Senate added it to the debate agenda, said Mr Somchai, an appointed senator.
However, timing could be a problem as the opposition is also expected to hold its censure debate on Nov 26-28.
The Senate speaker, who is also Senate chief whip, has asked the government chief whip to set a date for the general debate. It looks set to proceed after the censure debate, which is expected to wrap up on the morning of Nov 28.
Mr Somchai said if the government schedules the general debate on Nov 28 after the censure debate is concluded, there would not be enough time for the senators to speak. A later date is not possible as Nov 28 is the last day of the current parliamentary session.
He said there is no guarantee the censure debate will end in the morning, leaving a tight general debate schedule that he says belittles the senators.
Mr Somchai said the general debate should be carried out before the censure debate begins. The senators deserve the opportunity and adequate time to vet the government's performance, he said.
The senator said he also wanted Prime Minister Yingluck Shinawatra, Deputy Prime Minister Chalerm Yubamrung and National Security Council (NSC) secretary-general Paradorn Pattanathabutr to discuss reports of an assassination plot against Thaksin.
He said he felt uneasy about remarks by key government figures claiming an assassination plot was hatched against the former premier. It was supposed to take place during his planned trip to Myanmar's Tachilek town, which he has since called off citing security concerns.
The deputy prime minister has ordered the NSC and Provincial Police Region 5 Office to follow up on the reports.
"If someone [actually] wanted to kill Thaksin, the plot would not have been leaked," Mr Somchai said. He urged the government to bring Thaksin back to face the courts.
Opposition chief whip Jurin Laksanavisit said the Democrats will raise a fresh motion asking the government about the rumoured assassination plot.
The opposition had strong doubts about the existence of such a plot, as the NSC had earlier denied the report's plausibility, said Mr Jurin.
The opposition will tomorrow file a petition seeking the impeachment of some cabinet members with the Senate speaker, and will file a motion on Friday with the House speaker for a censure debate. The charter requires the opposition to file impeachment proceedings against ministers who will be grilled.