Minister of Education Nataphol Teepsuwan said on Tuesday that 34 out of 42 of the school's branches faced complaints via the OPEC.
Most of the complaints were about severe punishment, unlicensed teachers, and charging parents fees not allowed by the ministry.
Nataphol has told the OPEC to check the issues and take appropriate action.
He said that the most important issue of Sarasas Witaed School this time was about an alleged abusive teacher, Onuma Ploadprong, at the Ratchaphruek branch in Nonthaburi province, as well as other cases found later.
The minister added that his ministry prohibits teachers from punishing their students, and the legal punishments consisted of warning, placing on probation, cutting educational scores, and holding correction activities.
Nataphol also said that education officials found initially that Sarasas Witaed School had assigned babysitters to be teachers. The minister warned that this was illegal. If the school's alleged illegal activity is proved, the assigned babysitters will be imprisoned for two years and the school director for three years.
He said that he had told the OPEC to keep an eye on issues at private schools across the nation.
Last week, Sarasas Witaed Ratchaphruek School came under the spotlight after CCTV recordings showed kindergarten teacher Onuma physically assaulting children by banging their heads on their desks, pushing them to the ground or twisting their ears until they screamed in pain.
A recent video published online on Tuesday showed the teacher dragging a child along the floor by the collar.
The subject is still a hot issue on social media, with some netizens sharing their personal experiences of abuse in school, making the point that this problem needed to be addressed as soon as possible.
Some social media users see the abusive problem as the tip of the iceberg in the Thai educational system.