This is the process that it took to go from Koh Chang, Thailand to Siem Reap, Cambodia overland in one day. It was a really long day, but you'll be able to get a great view of the Thai countryside, but by the time I got to Cambodia, it was already too dark to see much there.
- 0600 - Wake up and pack
- 0630 - At reception, ready to check out. I asked the night before, and they said that it wouldn't be a problem to check out that early, but nobody showed up until
- 0730 - Checking out from the hostel on Lonely Beach
- 0800 - Taxi to Centerpoint ferry from Lonely Beach - 100 Baht/person
- 0900 - Arrive at the ferry and buy tickets to mainland - 70 Baht/person
- 0930 - The ferry leaves Koh Chang
- 1015 - The ferry arrives; disembark and catch a Songthaew to Trat bus station - 50 Baht/person
- 1115 - Arrive at the Trat bus station
- 1130 - Catch the slowest bus ever to Sa Kaeo - 185 Baht/person
- 1645 - Arrive in Sa Kaeo & buy bus ticket to Aranyapathet - 43 Baht/person
- 1745 - Bus to Aranyapathet departs
- 1830 - Arrival at Aranyapathet, catch a tuk-tuk to the Thai/Cambodian border - 80 Baht
- 1840 - Arrival at fake Cambodian visa office. Calmly argue that I know it's fake, until getting out of the tuk tuk to walk to the border.
- 1855 - Arrival at real border and go through all the entry processing. - 20 USD/person
- 1930 - Catch a shared association car with 4 people total from Poipet to Siem Reap - 400 Baht/person
- 2130 - Arrive in Siem Reap & argue with the driver about bringing us to our guesthouse rather than selling us to the tuk tuk drivers for them to take us wherever they want
- 2150 - Arrive at our guesthouse safely
In summary, the travel stated at 8am and lasted until 2130, making for 11.5 hours of straight travel time, and a cost of 928 Baht/person (plus the visa fee). This would have been further complicated (and more expensive) if I didn't do proper research about all the scams that can potentially happen when crossing the border from Thailand to Cambodia. That is my strongest recommendation for anybody going across the Poipet/Aranyapathet border--read about all the potential scams! I avoided losing money and time to at least 3 scams (1-Direct tours from Koh Chang to Siem Reap, 2-Fake Cambodian Visa office, 3-Getting sold to the tuk-tuks outside Siem Reap) during my 11.5 hour trip by knowing what they could be ahead of time. Just do 10 minutes of online research (I'll get you started here.)
If anybody has anything to add, or wants to share their experiences with this trip/the border crossing, please contribute in the comments!