@Ad**
, IF you board your airline comin' here you aren't going to have a problem with passport control stamping into thailand.
Like I said, it's getting on the airplane without a visa to thailand that requires proof of onward travel most of the time.
Now granted the passport control people here can ask you to show proof of funds, proof of onward travel, proof of hotel booking,
BUT
if you don't have an extensive history of living here on visa exempt or tourist visa entries, they aren't gonna say anything to do you when you stamp in.