score:8
Fly. Thai AirAsia has direct flights from Bangkok (Don Mueang) to both Siem Reap and Phnom Penh, and promotional fares can be less than 1000 baht all in - cheaper than any land transport option, and much faster, safer and more comfortable. Immigration at the airports is also virtually hassle-free.
The caveat is that regular/last minute fares are not particularly cheap, so you'll need to plan ahead to maximize your savings.
Upvote:9
Surface crossing from Vietnam into Cambodia is much more convenient than from Thailand into Cambodia. From Thailand, you feel like you are in a John Burdett novel -- it's a maelstrom of corrupt officials, scammers, and heat. From Vietnam, you feel like you are in Joseph Conrad novel -- it's a little compound of white-washed shacks hidden in the jungle.
Only time I crossed Cambodia-Thailand, I took a cab from Siem Reap to the border, walked over (waiting 30 minutes at Thai Immigration), and caught a mini-van to Bangkok. It took all day and was so uninteresting, I decided next time I would fly.
Only time I crossed Thailand-Cambodia, I took a bus from Bangkok to the bus stop in Aranyaprathet, paid $2 for the 10-minute ride to a "visa station", where they tried to scam me, walked over (waiting 30 minutes at Thai Immigration again), spent another hours dodging touts and scammers trying to find Cambodian Immigration (where they seemed very surprised I had found them), and then caught a cab to Siem Reap. It took all day and was so interesting, I decided to never ever do it again.
So, yeah, fly out of Siem Reap.
Upvote:10
Cheapest option is to take a train from Bangkok to Aryanaprathet (town on the thai side of the border), then go to the immigration office, then cross the border, then get to cambodian side (Poi Pet). Now you just have to avoid scammers, don't trust anyone who don't have a police or immigration uniform. Buy your visa at cambodian immigration office, then pass the checkpoint. There's bus to go to Siem Reap but if you're lucky and like to bargain, you can take a taxi, from my personnal experience I paid 5$ for 1h30 ride.
Crossing the border by foot is as impressive as visiting Angkor Vat, it's maybe not recommended to do it with childrens or stressed people, I found it safe, but it's a big mess ! There's motorcycle and rickshaw everywhere, and change of driving side (thai drives left side, cambodian on the right) complicate the mess.
Worst things that can happen is to buy a visa at a fake police officer, although it would be a legit visa, but with a extra cost :)