I have been told, but I'm not too sure, that I will need an air ticket leaving Bangkok before I can get an COE. If so, is it possible to get a cheap ticket so I can get the COE then cancel it? Any ideas? Thanks.
TLDR : Answer Summary
To obtain a Certificate of Entry (COE) for Thailand, you do indeed need to provide proof of onward travel, which can include a ticket leaving Bangkok. Many users have suggested options like purchasing inexpensive onward travel tickets from various websites that allow for cancelation. Some also recommended booking flexible or refundable tickets, which can be cancelled after acquiring the COE.