Thai Prime Minister Paetongtarn Shinawatra's coalition government is on the brink of collapse after a leaked phone call between her and Cambodia's strongman ex-leader Hun Sen.
They were discussing a border dispute that has ramped up tensions between the two neighbours in recent weeks after a Cambodian soldier was killed in a clash in May.
Paetongtarn appeared to dismiss a Thai military commander in the 17-minute call shared by Hun Sen on Facebook on Wednesday.
She said the officer "just wanted to look cool and said things that are not useful".
She defended the call as a "negotiation technique" but opposition figures are calling for her to resign, saying she has undermined the Thai army.
Bhumjaithai, the second-largest party in her ruling coalition, quit the alliance on Wednesday after the leaked phone call, dealing a major blow to her Pheu Thai party's position in parliament.
The coalition now holds a slim parliamentary majority - which will be lost if more of its partners decide to leave.
Two other parties in Pheu Thai's coalition are set to hold meetings on Thursday to discuss the situation.
The Shinawatras' friendship with Cambodia's Hun family goes back decades, with Hun Sen and former Thai Prime Minister Thaksin - Paetongtarn's father - known to consider each other "godbrothers".
Earlier this month, Paetongtarn said the close ties between the two political clans did not stand in the way of her defending Thailand's interests.
But critics have taken issue with her apparent deference during her call with Hun Sen, in which she addressed him as "uncle" and promised to "take care" of his needs.
Paetongtarn has said that she would no longer engage in private talks with the Cambodia leader.
Hun Sen said he had shared the audio clip with 80 politicians and one of them leaked it.
The border dispute has sent bilateral ties have plunging to their lowest in more than a decade.
Earlier this week, Cambodia banned a range of imports from Thailand, ranging from fruit and vegetables to electricity and internet. Cambodia had also earlier banned Thai dramas from TV and cinemas as a result of the border dispute.
Both countries have imposed border restrictions on each other.
The dispute between them dates back to more than a century, when the borders were drawn after the French occupation of Cambodia.
Tensions have flared up on a handful of occasions in the past. And in May this year, troops from both countries briefly exchanged fire at a contested part of the border, leading to the death of a Cambodia soldier. Both countries have blamed each other for the incident, claiming self-defence.