We hired a guide for 2 days. You get 8 hours for a very reasonable price. You determine your itinerary and you have all inflexibility you want.
Our guide was Nina and she was great.
She knew. A lot, was flexible and funny and showed us some of the typical highlights, but also brought us to some local restaurants and we ended with a great Thai boxing match were she was able to get us on the picture with the winner of the main match.
We had many guides in different places, and Nina ranked in the top!
Also the communication with the management went very well, always responsive.