By Plane

Low-cost carriers Air Asia and Jetstar Asia now fly to Siem Reap from Kuala Lumpur and Singapore respectively, but the popular route to Bangkok is still monopolized by Bangkok Airways, which charges accordingly (around $350 US per person, round-trip for the 1-hour flight). Thai Airways has begun service from Bangkok as of 2009.
The airport is less than 15 minutes from the town centre by car (US$7) or motodop (US$3 or less). If you have an advance booking in a hotel, you can ask them for a free airport pickup (in one of their tuk-tuks). This way you can avoid the monopolistic taxi service in Siem Reap.
There are separate terminals for international and domestic flights. International departure tax is a steep US$25 (children US$13), payable after check-in and before clearing immigration. Often this can only be paid in cash, as the credit card facility is unreliable. Airport fee upon departure on national flights, to Phnom Penh, is US$6.
There are separate terminals for international and domestic flights. International departure tax is a steep US$25 (children US$13), payable after check-in and before clearing immigration. Often this can only be paid in cash, as the credit card facility is unreliable. Airport fee upon departure on national flights, to Phnom Penh, is US$6.
By Lane

Whichever route you take, beware of scams, touts and pickpockets at border crossings, especially Poipet; see the Poipet article for information on the irritating Visa on Arrival process. Once you’re through all of that, take the free shuttle bus from outside the entry stamp office in Poipet to the transportation depot about 1 km away or find a taxi driver close by to begin bargaining.
An alternative is to take the official bus for US$10/person. The bus leaves when full – and only then, even if it takes a few hours – and can take about 15 people, with all the bags on the back seat. Extra people will be squeezed onto the back seat if necessary, which might not be so comfortable. Two fold down seats in the centre aisle are also not so comfortable. The trip is advertised as taking 3-5 hours, but in reality it takes at least 6 hours when the road is not too bad. An enforced stop after 2 hours at a restaurant can add to the time of the trip, depending on how long the driver wants to stay. There is the possibility of additional delays (e.g. “mechanical faults”) and these are almost certainly due to the same reasons as the Khao San scam-bus: getting you to Siem Reap late, tired and ready to take whatever guesthouse you’re delivered to. If you are sharing a taxi it will cost only a few dollars more than a bus and will be a lot better.
Alternatively, you could join the backpacking masses and pay a couple hundred baht for an uncomfortable bus ride directly from Khao San Road all the way to Siem Reap; any travel agent in Bangkok will be happy to sell you a ticket. Buses leave Khao San Road around 8 am and arrive in Siem Reap between 5 pm and 3 am. How long it takes exactly does not really depend on road conditions, but on the mood of the driver. Because he can “sell” you to a guesthouse in Siem Reap he will try to arrive there as late as possible, because if you are tired and afraid of walking around in Siem Reap late at night, his chances increase that you will stay at the guesthouse of his choice. (There is no obligation to stay, regardless of what the guesthouse owners tell you.) Even if you start in Bangkok on a big aircon bus, you will almost certainly find yourself in the back of a pickup or stuffed minibus for the Cambodian part of the journey. For the return trip, expect to pay around US$11.
Instead, take a bus to Aranyaprathet from Bangkok’s Norther Bus Station (Morchit). First class and second class buses leave from the ground floor of the terminal approximately every half hour with ticket costing 207 Baht and 160 Baht respectively. If travelling in the other direction, the last bus to Bangkok leaves Aranyaprathet at around 6:00 pm. The trip takes four to five and a half hours but be mindful that the border crossing closes at 8:00 pm and if you arrive too close to closing time there is a chance you will be requested to provide extra american dollars before they will process your visa. Also be mindful that the shuttle bus to the transport depot ceases to run before the border crossing shuts; if you find that you have arrived too late you will need to find a taxi to drive you the 2 hours to Siem Reap
From Phnom Penh

Most tour buses stop for a break half way between Siem Reap and Phnom Penh at Kompong Thom.
By boat

A word of caution: If you find yourself taking the boat/bus and person asks for your name to have his friend pick you up, he is in actuality selling your name to a tuk-tuk driver in Siem Reap. This is a fairly convenient way to get from the port to Siem Reap, just be prepared for an extremely hard sell to one of his select guest houses, restaurants, etc. If you just “roll with it” he will take you to a guest house and you will quoted US$10 for a normally priced US$6-8 room. Since the tuk-tuk driver has now pinned you for a “sucker”, he will try to sell you on his services to the temples for about US$15-20 a day. Be firm, and negotiate, they will bend towards the market rate. You’ll never really be ripped off, but keep in mind that if you are staying for longer than four days, that tuk-tuk surplus would be much better served through a charitable donation.