The Senate Speaker has submitted petitions asking the Constitutional Court and the National Anti-Corruption Commission (NACC) to relieve Prime Minister Paetongtarn Shinawatra of her duties following the leak of a recent telephone call with Cambodian Senate President Hun Sen.
The official letter asked whether Prime Minister Paetongtarn had committed corruption by willfully violating the constitution or laws, or seriously breached ethical standards.
Simultaneously, a request was submitted to the Constitutional Court under Sections 170 and 8, to determine whether Ms Paetongtarn's tenure as prime minister should be terminated in accordance with Sections 170(1)(4) and 160(4) and (5).
This development stems from a motion filed by Gen Sawat Tatsana, senator and chairman of the Senate's military affairs committee, who gathered signatures from fellow senators on Thursday calling for the prime minister's removal.
They accused her of lacking ability and credibility after she confirmed the veracity of the leaked audio clip.
The conversation included derogatory remarks about the commander of the 2nd Army Region, branding him an adversary, as well as a submissive tone towards the Cambodian strongman, in which Ms Paetongtarn signalled readiness to comply with Hun Sen's demands -- an act viewed as a serious affront to Thai national interests, they said.
Meanwhile, discord among coalition parties has left the Pheu Thai-led government shaken, with the United Thai Nation Party (UTN) becoming the latest member to speak out.
The party will now urge Ms Paetongtarn to resign amid mounting political pressure stemming from the leaked audio clip.
The UTN has proposed that Chaikasem Nitisiri -- one of Pheu Thai's prime ministerial candidates -- should assume the premiership if Ms Paetongtarn steps down.
Calls for Ms Paetongtarn's resignation have intensified following the departure of the Bhumjaithai Party, which has 69 seats. This has reduced the coalition's parliamentary strength to approximately 261 seats out of 495 -- raising fears of a minority government.
Three coalition partners convened urgent executive committee meetings on Thursday evening to determine their stance. Two of them -- the Chartthaipattana Party (10 seats) and the Democrat Party (25 seats) -- announced their continued support for Ms Paetongtarn.
As for the UTN, internal tensions have become increasingly evident. Sources revealed that the party's executive meeting was conducted under a tense atmosphere and did not include the faction of 18 MPs aligned with Suchart Chomklin, a former labour minister.
UTN executives were said to be of the view that if it, too, leaves the coalition, a dissolution of the House of Representatives and a general election could benefit the People's Party.
Juti Krairiksh, a list MP and a UTN deputy leader, said:
"If the prime minister does not step down, the ministers from the UTN will have no choice but to resign from their posts," he said.
Should Mr Pirapan's faction -- comprising 18 MPs -- decide to withdraw from the government, the Pheu Thai-led coalition's support base would drop from 261 to 243 MPs, falling short of the House majority threshold of 247 seats.
In such a scenario, the government would no longer command a working majority in the House, placing its stability and legislative viability in jeopardy.
"There must be an opportunity for those involved -- both government leaders and Pheu Thai Party representatives -- to discuss and work through the issues," Mr Juti said.
He further noted that as the House of Representatives is scheduled to convene a new session on July 3, a resolution will need to be reached before then. By the time the parliamentary session opens, it should be clear whether the UTN -- which holds a total of 36 seats but is effectively divided into two factions, one aligned with Mr Pirapan -- will remain in the government or move into the opposition block.