The rejection of two high-profile picks for the charter court, Siripan Noksuan Sawasdi, a renowned political scientist at Chulalongkorn University, and Chatri Atjananont, a former ambassador, has cast the Senate in a bad light and raised questions about its impartiality.
The Senate's "no" to both well-qualified candidates again plunges the institution into a crisis of trust.
There is no need for further proof that the Senate has an image problem.
Almost a year after it entered office, scandal after scandal has emerged.
There are accusations about its performance, such as that it lacks transparency and accountability regarding its previous sanctions against several candidates for independent organisations without clear reasons.
Meanwhile, its alleged affiliation with the Bhumjaithai party (BJT) has earned it the nickname the "blue bloc" chamber.
Currently, the Department of Special Investigation is investigating complaints about money laundering and other misconduct involving more than 100 senators during the June senatorial election.
Altogether, 11 candidates applied for two vacancies to replace two charter court judges whose tenure is about to expire.
A selection committee chaired by Supreme Court president Chanakarn Theeravechpolkul unanimously endorsed Ms Siripan and Mr Chatri. House Speaker Wan Muhamad Noor Matha and opposition leader Natthaphong Ruengpanyawut are among the panel members.
By rejecting the two candidates, the Senate fails to conform to political etiquette, which is to show respect to the selection panel.
Indeed, the Senate owes a public explanation for its dubious decision. It's not easy to find candidates with equivalent qualifications.
Initially, it was rumoured that only Ms Siripan, a pro-reform academic, would be left out in the cold due to her political attitude, given she signed a petition several years ago to amend Section 112 of the Thai Criminal Code, also known as the lese-majeste law.
But the Senate turned down both, 43:136 votes for Siripan and 47:115 for Chatri. Such a voting pattern draws suspicion even among the far-right, conservative elements.
It has only lent weight to the suspicion that the blue-bloc senators are meant to pick the candidates that are "us" and not "them".
It is speculated that the senate may prefer two other candidates, Sarawuth Songsiri, former highway department chief, and Surachai Kan-asa, former governor, who failed to pass the final screening.
Both are said to be close to BJT leaders. Mr Sarawuth was promoted to the top of the highway department by then Transport Minister Saksayam Chidchob; while being an ex-governor, Mr Surachai must have good ties with BJT, which oversees the Interior Ministry.
Now, the selection panel will have to start the process again.
While both Ms Siripan and Mr Chatri cannot reapply for the position, Mr Sarawuth and Mr Surachai can return as candidates.
However, unlike Ms Siripan and Mr Chatri, their knowledge and experience are not relevant to the job description, which requires experts in law and political science.
Yet, it's an open secret that political parties are in dire need of controlling independent agencies, from the charter court to the National Anti-Corruption Commission (NACC) and Election Commission (EC), the Constitutional Court, etc, out of fear of intense lawfare.
These independent bodies handle cases related to politicians, and their decisions can make or break careers.
Look at ex-premier Srettha Thavisin's downfall in August 2024 following a ruling by the Constitutional Court.
Mr Srettha was forced to leave office after the court ruled that his appointment of a minister convicted of serious corruption breached unethical standards. He was the country's fourth prime minister dismissed by the court in 16 years.
A year earlier, the Constitutional Court ordered the Move Forward Party to dissolve its electoral campaign, which the court found to undermine the institute of the monarchy.
Before that, Somchai Wongsawat, Samak Sundaravej and other politicians faced similar fates and were removed.
Such power is crucial as a political party that can wield influence over the Senate stands a good chance of being a coalition leader after the next election.
It would be no surprise if the Senate approved candidates affiliated with a political group such as the BJT.
Some political elements may find the blue bloc senate's role acceptable, seeing it as a balance of power with Pheu Thai and the People's Party.
Such balance may prevent the two parties from gaining absolute power.
Yet, such a power game does more harm than good. It only reduces public trust in the establishment and how the country is governed.