Easy if you respect the rules. 60 days + an extension of your Visa Exempt at your nearest immigration office. Take all documents, 1 photo, proof of residence ( hotel/lodging bill) fill in form , 1900 baht in cash. Go a few days before your visa Exempt runs out. Then leave country , do the same again. Careful with how you dress, speak nicely and you'll be fine. Doing this multiple time will probably not work. No need for an agent that will cost you.

@Phil *****

DTV isn't worth it for 3 months.

@Aaron ********

, Asso Kork is correct.

@Paul ******

exactly !!! If the author wants to stay a long time then he just get the appropriate Visa. As it is he is " abusing" the system.