I was told in Boston I needed a Visa or return ticket to go to Thailand. I convinced them I didn’t and they finally let me on the plane. At immigration in Chiang Mai they stamped my passport for the 30 days and no POOT needed.
TLDR : Answer Summary
The original poster managed to board a flight to Thailand without a return ticket or visa, receiving a 30-day stamp upon arrival in Chiang Mai. Other commenters shared their experiences, highlighting that many airlines like Delta may ask for a return ticket or visa but that some travelers have successfully bypassed these requirements. It was noted that proof of onward travel is often required by airlines to avoid costs on repatriating passengers denied entry.