USA law states that any air ticket is fully refundable within 24 hours. Buy ticket from USA airline if you go that route. Working online is a grey area, but I wouldn't mention it.
Consider a bit of time outside Thailand. - I call it exile:) I know its probably not what you want to hear though. I just received my 6th TR visa from Vientiane just 2 weeks ago with no red stamp or problems at the border. BUT - I regularly spend 2-4 weeks away from Thailand on my visa trips.
Its all about appearances - in out visa runs and no time outside Thailand makes it appear that you are working, which is what they care about.