Confused - the 30 days is not a "VISA on ARRIVAL" that is a different thing altogether - it is a waver of visa requirements.
I did not say "don't bother" - the immigration and tourist rules in Thailand and the way they are enforced are extremely variable and hard to understand - the most important thing is it is down to the discretion of thew immigration officer in front of you.
A friend entering from Oz had a problem as he had no return flight...this was because he was SAILING back - this took some time to explain but it WAS explained in the end.
Why would they accept your 60 day flight interval? Because they know you can do a visa run and you don't intend on living or working in Thailand.
I would be interested to hear from anyone who had been turned back solely because their return ticket was over the visa limit. Most tickets the second / other flights can be changed anyway - so if you're worried, why not get the return flight put down as 30 days and change it later?