To get from Koh Kong to the border at Cham Yeam (daily 7am–8pm), a 20min trip, it’s easiest to take a moto or tuk-tuk ($4/$10; note that prices from the border into Koh Kong are significantly higher). Taxis for Cham Yeam leave from the transport stop 2km west of Koh Kong, beyond the disused warehouse. Once across the border take a minibus (20m beyond immigration, on the right-hand side; departs every 40min 7am–5pm approx; 120 baht) to Trat where good a/c buses leave regularly for Bangkok (270 baht; 6hr) and other major destinations across Thailand.
There are a couple of scams to watch out for – the attempt to charge 1000 baht (around $30) or more for a visa when entering Cambodia, with the excuse that “This is a land crossing, it’s different”. No it isn’t! A Cambodian visa is $20 regardless of where or how you enter the country. If this happens to you, ask for a receipt; record the time, date and the name of the border official (or jot down the number on his shoulder) and report it, as soon as you get the opportunity, to the Ministry of Tourism (023 884974, [email protected]) and the Immigration Department (t 017 812763, [email protected]). Other scams include a bogus “quarantine station” beyond Thai immigration (you do not need any health forms to get your visa) and touts offering to “facilitate” the visa process by filling your forms in for a fee (anything from 100–300 baht); politely refuse as this is nothing you can’t do yourself. You can avoid all these hassles by buying your visa online.