No, you can get one if you have special skills required in Thailand. My application is based on invitation letter from a Bangkok hospital as my company are not present in Thailand
I hardly think the OP was bragging he is planning to work illegally, more naive that he did not know work permit is required which IMHO is ridiculous as so many people would do volunteer work so it is the Thai's that loose out not the volunteers.
Ho the hell is someone supposed to take a year out travelling supposed to explore Thailand if they say limit is 3 exemptions in 6 months. yes system has been abused by many but they now make it literally impossible to explore Thailand for long periods, they are just not interested in long term tourists. To mae things easier they may as well make it official, only one exemption per year. Then at least people would know.