Do I need a return ticket within 30 days or 60 days when entering Thailand on a Visa Exemption?

Thank you for your help, everyone. We are not going to list all the airlines up. OP needs to check with his airline about their rules.

Singapore airlines /Scoot will

ask. A few months ago they wouldn’t let me on the flight to Bangkok (from Manado) without an out ticket and I had to buy one on the spot for within 30 days. At Bangkok I was not asked and entered on 30 day exemption and renewed for another 30 days.

Technically, YES.

Entered Thailand in June with 30 day visa exempt and no return ticket. Wasn't asked by air carrier (Thai Airways) about return ticket. Immigration officer in Suvarnabhumi asked about it. Told her that I will travel with train to Nong Khai / Laos. She was fine with this information and stamped.

I thought the 30 day visa exemption had just become 45 days x

you are correct you can enter on a 30 day visa exempt entry and get one 30 day extension at the immigration office in the area where you stay for 1900baht

You are more likely to have problems with your air carrier checking in with onward travel in 60 days as some require you to have it within the number of days you'll be stamped in for if you are traveling without a visa and entering visa exempt.

Check with your air carrier, you won't have any issues at passport control stamping in to thailand with onward travel in 60 days