When exiting Thailand and then re-entering to "break the OA visa/extension chain" on a 30-day Visa Exempt stamp, are airport immigration officers requiring proof of onward travel within the 30-day period (i.e., airline ticket)?

There are reports that airlines have denied boarding a flight to Thailand if the person is not traveling on a visa and does not have proof of onward travel within the 30-day permission to stay (round trip ticket or ticket to another destination outside Thailand).