The link which Graham Heyes has posted is an agency website. It is well known amongst expats for posting misleading information and trying to tout their services. Be warned!
There's actually no such thing as a 30-day Visa On Arrival. You're actually entering with no visa, just a free 30-day entry stamp. There's no official limit, the only instances where immigration will pay close attention is when people are doing back to back border bounces to remain in the country for long periods with no visa. Many FIFO workers use the free stamp with no problem, because they're in and out the whole time and are not spending long uninterrupted periods in Thailand. If you're coming three times a year, spread out through the year, you'll have no issues
TM30 has nothing to do with 90-day report. Your 90 day report date is governed either by your date of entry into Thailand, or 90 days from the previous 90-day report. The TM30 is registered each time you move address outside of the province in which you're residing. The TM30 app is excellent as it takes about 30 seconds to complete whilst you're sitting at home. It sure beats traipsing to the immigration office to do it. But of course, I always emphasise that it's each to their own, and whatever someone is most comfortable with