I haven't visited Thailand since the new visa regulations went in to effect, but I'm planning a trip for December for several months. I would like to get a 60 day tourist visa at the consulate in New York. At the end of the 60 day period I'd like to visit an expat friend in Cambodia for 2-3 weeks and then fly back into Thailand from Phnom Penh, Will I be able to get a 30 day visa on arrival tourist visa when I land in Bangkok? At the end of the 30 days I'll be returning to the states.

Yes, that will be no problem.

(But you actually get a visa exempt entry, not a visa on arrival. That is something different).

I haven't visited Thailand since the new visa regulations went in to effect, but I'm planning a trip for December for several months. I would like to get a 60 day tourist visa at the consulate in New York. At the end of the 60 day period I'd like to visit an expat friend in Cambodia for 2-3 weeks and then fly back into Thailand from Phnom Penh, Will I be able to get a 30 day visa on arrival tourist visa when I land in Bangkok? At the end of the 30 days I'll be returning to the states.

Actually there are no new visa regulations. You will receive 30 days visa exempt, not "visa on arrival tourist visa"

My folks got a tourist visa; visited me for a couple of months and then flew to see my brother in Australia for 3 weeks and just got back to Thailand to stay for aother fortnight before flying back to.the UK. Came in on a 30 day visa exempt no problem.

Yep, I haven't heard of any new visa regulations...