Big problem is we don't know for sure because everyone's travel history is different. All I can do is explain what happened to me these last few months trying to do exactly that and say it seems to be increasing. I was told I cannot stay 5 months as that is 'not behaving as a tourist' whatever that means. You could have no problems for your first 5 months but try that year after year and u could be stopped and questioned eventually.
I will get a NonO based on retirement before I come back in Nov for sure. I do wonder like you if my long time working here is now going against me. But they clearly knew on my arrival on day one I planned to stay 5 months Nov to March. Probably from my flight bookings. That may also have been an issue but it wasn't last year.
if you are not a member already join the Thai Visa Advice group page on FB. Just read all the stuff there over a few weeks about all the Imm problems nowadays. Follow a guy called Tod Daniels or any of the moderators there. I learnt all my knowledge from them. They are well on top of Visa info
just posted my story in reply to Todd McGowan. I came back into Thailand at Nong Khai border with no hassle at all. I flew to Luang Prabang and planned to fly back but was advised not to do that as I had been grilled 3 times already. Nong Khai is the easiest border by far. But next year I will get a NonO visa for sure.