Looks like they have some long term standing advisories about the very southern tip....
From the US site:
http://travel.state.gov/content/passports/english/country/thailand.html
The U.S. Embassy prohibits its personnel from traveling to the far south of Thailand – specifically, Narathiwat, Pattani, and Yala provinces -- without prior approval, and Embassy personnel may go there only on work-essential travel. U.S. Embassy and Consulate personnel must provide advance notification of travel to Songkhla province, and they are advised to use hotels outside Hat Yai’s central business district. The Department of State urges you to defer non-emergency travel to these areas. If you must travel to these areas, you should exercise special caution and remain vigilant with regard to your personal security. You should be aware that martial law has been in force in the far southern region since 2005, and Thai authorities have on occasion instituted special security measures in affected areas, such as curfews, military patrols, or random searches.
From the UK site:
https://www.gov.uk/foreign-travel-advice/thailand
The Foreign and Commonwealth Office (FCO) advise against all but essential travel to the provinces of Pattani, Yala, Narathiwat and Songkhla on the Thai-Malaysia border. On 10 April 2014 the Australian authorities indicated that extremists might be planning to target westerners in the southern border provinces. See
Terrorism
But one has to keep all of their ass covering warnings in perspective....I go to India all the time....they have travel warnings about parts of India too!