I was looking for a custom tour with a specific and unusual focus...I wanted to do home stays and arrange for local musicians to perform traditional Thai and hilltribe folk music.
I first contacted the top rated village home stay tour provider on Trip Advisor: Thailand Hilltribe Holidays. I don't know how they've earned their rating, but they were curt and unhelpful, completely disinterested in any actual customization to my interest. They told me arranging music performances would be next to impossible, but I got the sense they just didn't want to do any extra work beyond their pre-arranged tours to cater to my goals.
Then I tried Next Step Thailand and had the opposite experience. Samart bent over backwards to quickly arrange exactly the tour I wanted. He started with my priority, musical performances, and even though this had not been requested before, he managed to leverage his local contacts to arrange a private concert for every night of my tour (all of which were high quality, wonderful performances). And he arranged the entire thing in less than 48 hours of my initial request. My guide, Wasan, was extremely helpful and a fun tour companion. He translated conversations with the musicians, and even arranged for me to take a lesson with one of them, mixing up our itinerary last minute to accommodate an extra detour.
Next Step deserves the top rank IMO, and if you have any unusual interests you're pursuing you should certainly use them over Thailand Hilltribe Holidays.