Yes you may well have problems. On arrival at Bkk I was asked how long I was staying. My return flight was 90 days but I had a onward ticket for 60 days. On arrival they did ask to see the outbound flight and recorded it on my records. I then decided not to use the onward ticket as I am meeting somebody travelling to Bangkok around that time so I was thinking of an extension. I am now 47 days in and a few days ago I got the chance to go to Poi Pet Cambodia for a couuple of days in a friend's car. Coming back into Thailand I got a real third degree grilling. Why wasn't I going to Singapore, the onward flight that I had and I was not taking, when was I coming to Thailand again, did I have a family in Thailand. I was just coming for 3 months, so just an addional 30 days. You are coming for 6 months so will need an extention another exempt entry and another extension or two more exempt entries. Given the problems I had just staying 90 days I would say you are going to have problems. They seemed to have really clamped down.