Each time I have left Auckland they have asked for a return ticket at check in, I have a long stay visa which doesn't require one, sometimes that's accepted straight away, other times they make a call, or a supervisor more aware will complete check in.
Genuine tourists rarely complain its those who don't go home and don't qualify for a long stay visa who aren't happy being denied entry as the pretend to be tourists but aren't able to fool every immigration officer by attempting continuous exempt entries .....
The "free" 2nd year you mentioned, will also require the mandatory OA insurance for that 2nd year, otherwise he will be stamped in until the insurance expiry date instead.
Point number 2, how I read it, if the OP already has the 800K seasoned in a Thai bank account, depending on his immigration office, he can go for his one-year extension, with 45 days left on his 90-day stamp in Chiang Mai for example.
Sounds like he doesn't need to use the first 60 days of the 90-day stamp for seasoning?
Your 1-year OA can be stretched to 2 years if you re enter Thailand just before the 1 year expiry date is up, then you will be stamped in for another year from the date you arrive providing your required insurance cover also extends through the 2nd year.
After that to extend in Thailand, your funds (800k THB) will need to be in a Thai bank.
Need to be mindful of your 90-day obligation, totally separate to visa extension dates, as unlike exiting the country, the 90-day clock does not reset when obtaining a new extension.
In saying that, sometimes an office will reset your 90 days at the same time if within the reporting window, they will tell you and provide a new slip. You too can report your 90 days whilst there with the usual paperwork but like Tod has said, without obtaining a new 90-day receipt at the time of your extension, then presume it wasnt reset.