Despite the government's efforts to crack down on corruption in state agencies, the practice of paying bribes to secure school places is said to be rampant.
An allegation that Samsenwittayalai School director Viroj Samluan demanded 400,000 baht in pae jia, or "tea money", from a parent in exchange for enrolling his child at Matthayom 1 (Grade 7) at the school hit the headlines last week.
The case reignited public concern, with demands made for the government and its Education Ministry to investigate the allegation and step up efforts to eradicate the practice of parents paying school directors for favourable decisions.
Mr Viroj denied the accusations, but has been reassigned to work at the Secondary Educational Service Area Office 1 while the investigation is conducted. He has not been removed as the school's director.
The Anti-Corruption Organisation of Thailand (ACT) has urged the government to force school directors nationwide to declare their assets to avert possible graft accusations in the wake of the Samsenwittayalai scandal.
ACT director Mana Nimitmongkol said parents should not be allowed to use their personal connections or financial means to get their children enrolled at any school, adding that asset declarations would stop school directors from operating such a system.
"School seat trading is now common knowledge among parents," Mr Mana said. "It may not be called tea money directly; it could be a pledge of donations for school development.
"Such payments are in the mid-five figures [in baht] range for less popular schools and can go up to six and seven figures for some prestigious schools."
Mr Mana said he had no problem with school donations, but they should be made without the expectation that a donor's child will be guaranteed a place at any particular school. Also, all donations should be transparent, he said.
"My recommendation is that receipts must be issued for every donation so all such transactions stand up to scrutiny," he said. "All donations must be posted on school noticeboards and websites, so donors can check where their money has gone and how it was spent."
The ACT director also urged the Education Ministry to narrow the quality gap between prestige schools and medium-sized schools, as this is one factor that contributes to the tea money problem.
"The pae jia system is a byproduct of social disparity," he said. "The quality gap between famous schools and normal schools is too wide. That's why many parents are willing to pay an exorbitant amount of money to purchase a seat for their children in well-known schools."
Mr Mana warned this kind of mindset is dangerous as it can instill in children the idea that corruption is acceptable or that the wealthy can take advantage of the poor.
"Parents are role models for their children," he said. "If the parents are corrupt, there is a high chance that their kids will be the same."
Mr Mana said parents should change their belief that academic success and a foot on the career ladder can only be achieved by attending famous schools. "I understand this is a stressful game all parents must play, but if your children fail to attend your preferred school, it's not the end of the world," he said.
Athapol Anunthavorasakul, an academic from Chulalongkorn University's Faculty of Education, said: "There is no guarantee that graduates from famous schools will be good citizens or successful people."
Mr Athapol said he thought there is not much difference in term of teacher quality and educational tools between big and medium-sized schools nowadays, but the difference is the learning environment.
"The competition among students might be higher in famous schools, so the students need to be more active," he said.
"Parents should ask themselves how they define success for their children. Do they define it as getting a seat in a top university and becoming an engineer or a doctor, or does success mean your children are creative, critical and eager for lifelong learning?"
Mr Athapol said the average class size at most famous schools now is 50, while the average class sizes at "ordinary" schools is just 30, so if famous schools keep expanding their number of students to get more donations, this will harm the quality of the classes.
"You can see that today even students from famous schools need to attend extra tutorial schools,'' he said.
Mr Athapol said the parents' role is just as vital as that of their schools in creating quality citizens.
He said parents should be more than mere financial supporters for their children, they should also play an active part in their children's education.
"In developed countries, parent representatives can participate in almost every decision-making process at their children's schools, from lunch menus to curriculum planning, but in Thailand parent representatives are set up just for raising funds," he said.