The leaders of the eight coalitition partners led by Move Forward had previously agreed to meet on Thursday to prepare for the House opening. A new date has not yet been announced.
Despite being vaccinated six times, Pita reportedly contracted the virus during his recent trip went to thank voters in the North.
“On Sunday [June 18], I started to have a few symptoms. After that, I started to self-isolate," he wrote in a Facebook post on Tuesday.
He said he used a self-test kit and found he was infected on Tuesday.
Pita will not be able to join any talks for a while, including a meeting of party transition teams and a seminar for new Move Forward MPs set to take place on June 21-23.
Pita urged people who had come into contact with him to test themselves as a precaution.
Chaitawat Tulathon, the secretary-general of Move Forward, will fill in for Pita while he is absent.