Can I apply for a 60 day Tourist visa to Thailand with a one-way ticket?

You can get an O in Thailand not an OA

Expedia 👍

Book a flight to Cambodia/Vietnam for less than £30 print the proof and use the 24 hr cancellation option.

The Airline wit most likely refuse you boarding the flight as they are responsible for getting you back to your original destination if you are refused entry

Bus tickets and other forms of exiting the country are not guaranteed safe options

You'll need return or onward travel within 60 days for the Tourist visa plus you wont get a Non Immigrant OA visa in Thailand.

When booking at Thai Airways this warning appears:

“Passenger who hold only one-way ticket may be denied entry at the destination. Please ensure you are in compliance with the entry requirements and regulations at your destination before payment.”

You cannot apply for a OA visa in Thailand, it must be applied for in your home country.

You can only apply for a Non OA visa in your home country.

Your airline will be the one that may have issues with a one way ticket. The online visa process will probably be a stumbling block too.

On a tourist visa you must show airlines and sometimes immigration that you're leaving the country within 60 days. Bus, train, plane, etc., to anywhere outside Thailand.