I'm trying to plan a multi-country S.E. Asia tour. While I like the idea of traveling from Phnom Penh to Vietnam by boat, I don't necessarily want to spend several nights and $400+ doing so. (I'm traveling alone, and many of the better cruise options are priced per person with double occupancy.)

Anyone know any good, fast options for the above route? I don't necessarily want to take a speedboat, but I'm trying to figure out what the fastest comfortable options might be. Thanks.