The troubles in November last year (with the airport blockades etc) caused some grief for travellers. For those who have to stick by strict schedules and don't like to risk trip disturbances (delays, diversions and so fourth), the latest round of political strife may present problems.
But for those who have some time and want to go to Thailand and the surrounding regions anyways, there may be bargains and nice quiet getaways. During times when tourists are hard to come by (whether it's bad weather, monsoon or political disturbance), many touristy locations become desperate for business. Basically it's a case of too many sharks and not enough fish.
I lived in the Gulf of Thailand during the Coup and subsequent martial law of 2006/2007 and from where I was, we were almost oblivious of the political goings-on. The only noticeable military presence on the island was a lone uniformed old man directing traffic on a street intersection. As I write, my friends and former colleagues are probably more concerned with the New Year celebrations than with any political crisis.
So if you go, just take precaution, avoid Bangkok and other potential flashpoints and look out for those bargains.