Arrived recently at Suv with a METV issued in the UK. After all the recent crackdowns was expecting to be questioned, as have been staying in Thailand for approx ten months every year for the over ten years using tourist visas. Had all the extras ready regards cash, hotel booking and onward flight within 60 days.
On arrival the IO looked at his computer screen and casually called the 'roaming duty officer' over. Understanding a bit of Thai i heard him stating to the other officer how long I had been in the country over the past years. Had visions of having to stay in their 'special accommodation' for a few nights.
The IO in charge looked in more detail re my past stays in the country and simply explained i was using the wrong visa, stating i should have an over 50 long stay non O. Didn't ask for any proof of funds, hotel booking or onwards flight. Said he would stamp me in this time without any problem - but also stressed that next time i came over i should make sure i have the correct visa.
My impression of the IO's was that they were very polite and understanding. They have a difficult job to do and at times it must be very stressful. However, when dealing with them keep calm, explain your situation clearly and they will try and help.