I think it's more about the time in between visits. If you're doing border bounces or leaving Thailand for 2 days for example and then coming back in you're going to invite trouble - if you're month on and a couple of months off you'll be right. That's what I did last year - and intend to do next year again. It just depends how you do it, and who you get at immigration on any given day. It's not an exact science.