you put the burden of proof on others. There is no source that the requirement of proof of onward travel has been dropped, and a gazillion sources proving it hasn't. I'm just not gonna spell them out for you.
you can reply 20 times to the same reply but it doesn't make you right. The rule has not been dropped. There's also no source for that; you reply from imagination. And then you put the burden of proof on others.
you should read more replies in this group and you'll find a couple of guys having been asked for proof of onward travel. It's not a lot still, but it's more than nothing. Keep in mind that any positive number of people being asked for it is already more than in the past.
Airlines are indeed still enforcing the rule. If it got dropped, they wouldn't.
it's not dropped. Quite the contrary: unlike before, we hear from people here who are getting asked to show it. What got dropped is the limit on two land border entries per calendar year.
well thought but unfortunately this won't work. You cannot do online check-in if you need a document check, which you need it you fly on a single ticket.
they may have said you didn't need to buy an additional ticket and interpreted your story as that you were in possession of a bus ticket to Cambodia. Airlines are not different in onward ticket requirements - it's not their policy, it's the Thai authorities policy that they do a pre-check for. And they're required to do that.
you're entirely wrong. Immigrations doesn't note anything down, and can't care less about whether you have an exit ticket or not. Doesn't matter, if you think they do you are on the safer side of things.
You are right that it would make sense if airlines just take more of an advisory role and keep the decision to wing it or not with the passenger. But that is unfortunately not how it works. They don't want to claim back expenses and fines they incur later. They want to prevent them. They're also committed to check entry eligibility, it's required by the Thai authorities (as it is by any country).
No, officially you can't. You can if you don't get checked, which both immigrations and your airline are supposed to. Immigrations normally can't care less, but with your airline this may be different. They also do not have watertight checking policies, but checks are quite common. If you get checked, they can't let you board with a one-way to Thailand.