Kathie,
I may have been off topic as I wasn't commenting on the practicalities of driving from Bangkok to Siem Reap, moreso just my own beliefs on driving in Asia in general.
I think it makes for an interesting enough debate for it to have it's own thread so I may start one so to seek other opinions and we can continue this conversation there.

Self driving

I would love to drive to Siem Reap....but as yet I have not heard of ANYONE who has actually personally done it in a private 4 wheeled vehicle both ways. I suspect the time approaches when this will be a more common occurence

- your problems are not the roads (4WD pickup should have no problems) or the other drivers...in theory it is possible but in reality it is bureaucracy that will win out and your idea will probably bite the dust.

The ASEAN treaty allows for transport to pass between member countries but it doesn't work that simply......if you enter Cambodia with the right documentation - (best if you OWN the car) you will find that you are only permitted to drive in the province you've entered - so going further leaves you open to all the vagaries of local corruption and banditry.....as for insurance etc etc......remember like their erstwhile French colonial masters they allegedly drive on the right too.....

Negotiating the borders at Aranyaphrathet/Poipet is a pain too - the place is like an old wild-west town and the locals want to keep it that way so they continue to make a nice living fleecing the tourists...everyone is involved from the agents and guides who profess to offer help to immigration, customs, police. As with visa runs, it's often best to just get someone from BKK who will do the lot for a fixed fee...that way you don't even have to confront any of the money-grabbing b*****ds at all.

PS - if anyone has FIRST HAND experience of self-drive there, I'd love to know

I think it's telling that the otherwise exhaustively comprehensive talesofasia.com doesn't even mention driving yourself.

You know as much as I like an adventure, I may shelve this idea and see if I can fly into Phnom Phen and rent a boat to Angkor Wat. That could be fun too.

You might want to read what talesofasia.com has to say about the boat trip. The bus is fine, or you can take a taxi if you want to get fancy.