Thailand's Bhumjaithai party, which left the ruling coalition last week, said on Tuesday it will seek a parliamentary no confidence vote against Prime Minister Paetongtarn Shinwatra and her Cabinet, in another blow to the embattled premier.

Next week's planned motion will be the first parliamentary test for Paetongtarn, 38, since coming under intense public pressure over her handling of an escalating border row with neighboring Cambodia, which has left the ruling alliance led by her Pheu Thai party hanging on to power by a thread.

Bhumjaithai withdrew its support for the government last Wednesday citing the risk of a loss of Thai sovereignty and integrity from the leak of a phone conversation between Paetongtarn and Cambodia's former premier Hun Sen.