I could be wrong but think there is a clause stated that customer needs to ensure to have proper travel documents.. bla bla bla before purchasing the ticket. The airline is not responsible.... You know, that kind of standard stuff.
airline ground staff has even more authority than immigration. That's a fact. They can deny your entry based on blacklist, no proof of outgoing flight, visa matters, damage on your passport... even smallest water droplet stain on your passport could be a reason if they want to deny you. So yea, be nice to your airline ground staff next time. š
Just curious. How does he renew his work permit for the past 15 years if he didn't renew his business visa? And if he did renew his business visa, why would he needs Covid extension and visa run? Hahaha. Are you sure he's been working the past 15 years?
After a few extensions, those officers will speak to you in Thai and expect you to reply them in Thai as well. Else they won't give you extension anymore.
Just buy a ticket and go home. Try entering Thailand again next time.
Although there are rules on how many border run or entry by air, I believe there is also a clause stating "It is at the discretion of immigration officer to approve or deny entry to the particular applicant if he or she believes ..... ".