Denied Entry at Phuket

Hello everyone
I arrived to Phuket from Japan without Visa and was denied entry by immigration. Currently Im being held against my will in stuff room kind of prison which I have to pay for (100thb/hour).
Some background informations:
– Im Polish (rules says I dont need Visa if my stay wont be longer than 30 days).
– I had ticket out of Thailand within 30 days which I showed to them
– I wasnt asked about funds for my stay (20K thb?)
– I already have 5-10tourist visas in my passport
– it was my first entry into Thailand without visa
Reason for denial wasnt clearly stated to me. From what I understood it was: suspicious activity (frequent Visa runs). Also from what I understood I will have to go to the same airport I came from and pay for the ticket.
Right now Im stuck in a prison room with no information. Security guard told me that airline stuff is coming (2hours ago) but no one showed up so far.
Can they keep me like that?
Shouldnt airline cover my ticket?
Can I book flight to other destination?
Im looking for advice. Any help is appreciated