Will airport immigration deny my entry if I return to Thailand after 60 days as a tourist?

Hi everyone, i would like to ask. I am a Singapore passport holder who came in to Bangkok as a tourist with 30 days stamp and then i applied for extension (paid 1900 baht) for another 30 days. My visa ends on 9 June. Qns, as i applied to study Thai in a school. I waited so long for them to process my visa while i am in Bkk. They told me that to leave Bkk before 9 June and come back on 12 June with a new 30 day tourist stamp and then meet them at immigration so they can change my visa from tourist to education. I am confused with the system. Will the airport immigration deny me entry? Seeing i had been in Bkk for like 60 days as tourist and then just gone for a few days and coming back again as a tourist?