@Ralph ******
so because an extension is not guaranteed, people are required to buy flights out of Thailand at a time they don't plan to fly? Despite that it is also just required to leave Thailand before your visa stamp expires, regardless of whether flights were pre-purchased or not, and this policy is enforced? And despite that having a flight within 60 days guarantees by no means that people will actually fly out? Also, if many flights can be postponed or cancelled? No sir, this is absurdity at its finest. The whole rule is absurd because it achieves nothing and it only a nuisance for many and causes sunk cost that Thailand doesn't even benefit from, but the fact that extendability is not accounted for makes it even more absurd. FYI, other countries such as Indonesia (where having onward ticket is enforced much more strictly upon entering and they require it even for 6 month visas) and The Philippines DO account for extendability.
There aren't many countries that don't have this absurd policy, but there's a notable example: Australia. Despite that they're strict with many things, at some point they appear to have realized how pointless requiring proof of onward travel really is, and they just stopped it. They only require it now for transit visas.