The Senate's impartiality has been questioned again after a majority of senators rejected two high-profile picks for the Constitutional Court.
Siripan Noksuan Sawasdi, a political scientist from Chulalongkorn University and Chatri Atjananont, a former director-general of the Department of Consular Affairs at the Ministry of Foreign Affairs, failed to secure half of the Senate's votes to replace two outgoing judges at the court.
Among 11 candidates, both were chosen by a selection committee chaired by Supreme Court president Chanakarn Theeravechpolkul, House Speaker Wan Muhamad Noor Matha and opposition leader Natthaphong Ruengpanyawut. The nine candidates who were rejected are high-ranking officials from ministries and the courts.
The Upper House's rejection raises questions about the criteria which senators use to select judges, high-ranked judges, and commissioners for independent bodies such as the Constitutional Court, Election Commission and National Anti-Corruption Commission (NACC).
Needless to say, the latest vote only raises more doubts about the upper chamber, especially as a few weeks earlier, the Department of Special Investigation launched a probe against more than 100 senators, some of whom were linked to political parties, for money laundering related to vote-blocking in the senatorial election last June.
Usually, it has been tradition and political etiquette for senators to approve names proposed by independent bodies. Yet during the past few years, senators in the majority bloc have turned down the names proposed by screening committees of those independent bodies.
Last year, the previous junta-appointed Senate rejected the NACC selection committee's proposal to make former Metropolitan Police chief, Pol Lt Gen Thiti Saengsawang, known for his clean image, a new commissioner.
In February, the current Senate disapproved of Ruenvadee Suwanmongkol, formerly secretary-general of the Stock Exchange of Thailand Office, who was nominated as ombudsman by the Office of the Ombudsman screening panel.
It remains a question why senators failed to endorse Ms Ruenvadee, a Harvard University law graduate with a track record at the Securities and Exchange Commission and Legal Execution Department.
The problem is the public does not get the chance to know why decisions are made. The upper chamber usually votes to pick candidates in closed-door meetings, like the latest one. Without a clear explanation and transparent voting process, rumours only gain ground.
So now there is no explanation for why most senators voted against Ms Siripan and Mr Chatri. News reports only described Mr Chatri as not being the "preferred choice" of most senators.
Meanwhile, it has been suggested Ms Siripan had an "attitude problem" because she signed a mass petition seeking to amend Section 112 of the Criminal Code, or the lese majeste law, a few years ago.
Unsurprisingly, there have been calls for a charter amendment to remove the Senate's power to pick executives of independent bodies. The recent decision only adds fuel to this idea.
The Senate needs to show it is impartial, professional, and, above all, free from intervention. The latest vote -- in a closed-door meeting -- only raises doubts about whether our senators are fit to do this crucial task.