The closest airport is on the Lao side of the border in Pakse, though it would be considerably cheaper and more convenient to fly into Ubon Ratchathani if coming from Bangkok.
The Northeastern line ends in Ubon Ratchathani, where you can head across town to the bus station and catch a minibus to Khong Chiam.
The few buses and more frequent minibuses that pass through Khong Chiam use a centrally located bus stop at the corner of Moo 1 and Highway 2173, across the street from the morning market.
From the bus terminal in Ubon Ratchathani, minibuses depart hourly from 06:00 to 18:00 and stop in Phibun Mangsahan before dropping passengers in Khong Chiam and continuing onto Chong Mek, Warin Chamrap and back to Ubon. The price to Khong Chiam is 80 baht and the ride takes around 1.5 hours.
We were told that minibuses do not run in the opposite direction, so if coming from Chong Mek you’ll probably need to take a roundabout ride through Ubon, or hire a tuk tuk for around 300 baht.
One bus departs for Mukdahan each morning at 06:00. At least one daily bus also runs all the way here from Bangkok’s Morchit station, picking up in Khong Chiam at around 16:00. Bangkok and a host of other destinations can also be reached by transferring in Ubon.
Khong Chiam is a small town that’s easily explored on foot. To hit the outlying attractions, you can hire a tuk tuk or rent a motorbike for 300 baht per day at Baan Steak, a small restaurant next to Once Upon a Time Cafe on Moo 1. A tuk tuk driver quoted us 1,200 baht to take up to four people to Pha Taem National Park, including Soie Sawan waterfall. Alternately, a tour of the park by car can be arranged at Ban Mongkhon and other guesthouses. See the Pha Taem page for more detailed transport info to the park.