Three adults will be flying into Don Mueang Airport from Siem Reap in the early afternoon on November 29. We have overnight lodging booked in Kanchanaburi for that night. What is the best way to get there?

I've been told a taxi is possible, but since this is a lengthy trip can we find a taxi at the airport willing to make this trip? Should we book a taxi in advance? Is train (or something else) a better option? Might we be better off just hiring a private car for the trip, obviously more expensive but we'd be ok with that (and if so can anyone recommend who to hire)?

In short, what's the best way to get three adults from Don Mueang to Kanchanaburi with the best combination of comfort and speed. We're all Americans who only speak English and Spanish and this will be our first time in this part of the world.

Thanks for any suggestions you have!