Ill be coming from either Bangkok or Pattaya. I want to arrive in either Phnom Penh or Sihanoukville.

Is there a bus from Poi Pet to Phnom Penh? How are the roads?

Im not sure how the trip from Trat works. From Hat Lek do I take a speed boat or a ferry to Koh Kong? How is the ride? Can I take a lot of luggage?

From Koh Kong can I take a bus directly into Sihanoukville?

There are plenty of buses from Poipet to PP in the morning until around at least 10 AM. In the evening there is a 8 PM (usually a little delayed) night bus.

The day buses are pretty good, I usually use Capitol bus. There are also joined taxi services which are more expensive. They do the trip within 5-6 hrs.

The road between Poipet and PP is pretty good. Between KK and the PP-Sihanoukville highway is considerably less good.

From the Hat Lek border to Koh Kong you need to take a motorbike. Public transport to PP either by morning bus or shared taxi. To SHV take a Van. The ferry is not necessary anymore (for at least a decade by now?).

You better show up with an e-visa (tourist visa over the internet) if you show up at Koh Kong. Otherwise you will be charged 1500 Baht.

If you need a visa type "'e" (business visa) you better go to Poipet and get it there or take a cheap flight to PP.

So there are no buses from 10 am until 8 pm from Poi Pet to Phnom Penh?

There is a bus from Bangkok to Phnom Penh that leaves 8 and 9 am every day. I heard there is an extra 800 bhat fee for crossing the boarder when taking this bus. Ive never been charged that on a visa run.

What is the cheapest airline? How long in advance to i have to book to get the cheap price?

air aisa, book in advance as far as u can.

You can change dates an see the fares.

voa for $30 book a seat for an extra 70 baht near the front

Usually around 3,500 r/t

It is been a while since I checked the departure times for Poipet. 10 AM i am pretty sure you get a us. After that I would be guessing.

There is no direct bus as far as I know right now. The direct service was introduced some 18 months ago but soon stopped. I might be wrong and it is running again. You could ask on one of the travel forums. The tickets some travel agents sell are not for a direct bus. They simply put you on the standard bus to the border market and then you get a connection on the other side.

Anyhow, you can always check for a joint cab (6 passengers) for PP. Price 15-25 USD depending on situation.

I personally like the train and taking it easy. You could take the 1 PM train from BKK for 48 baht to Aranyaprathet. Arrival at around 7 PM. You would have enough time to sort out your visa and make it to the Olympic Bus to PP at 8 PM. Or stay in Aran or Poipet for the morning bus.

Cost break down: train 48 baht, motorbike taxi to border 60 baht, motorbike taxi to bus 1 USD, bus 9 USD