You can reach the border of Cambodia from Thailand by land. You can either choose from a 4-5 hour bus ride or 6-7 hours train ride. We chose the former.
We woke up early the next morning to catch the casino bus going to Cambodia. We initially plan to take a cab but there’s nowhere to be found so we end up walking more than 2kms of what we have expected because the bus was relocated away from Lumphini Park.
Aranpayet and Poipet is the border of Thailand and Cambodia, the casino bus will drop you off to Rongkula Market and from there you just have to walk through the immigration of Thailand and Cambodia.
There have been numerous advice from fellow bloggers about scammers at the border of Thailand-Cambodia. First are the locals who will approach you and will tell you that you need to pay for visa. Second are the taxi drivers that will offer you pricey ride to Siem Reap. Fortunately, we did not meet both.
(you may check our budget and itinerary for this trip – Thailand, Cambodia & Vietnam Tour)