Pailin has a Paramount Angkor Express bus station a five-minute walk from Pailin Ruby Guest House. It's very close to Acleda Bank.
Paramount Angkor Express runs a service from Phnom Penh and Battambang.
T: (092) 575 572 (Battambang Office)
Phnom Penh departs at 07:00 and 07:30, costs $11 and takes 10 hours.
Battambang departs at 13:00, costs $4.50 and takes 2 hours.
There is no direct bus from Siem Reap, but you can catch a connection in Battambang.
A taxi to/from Phnom Penh should cost about $85, from Siem Reap $80, and from Battambang $45.
Paramount Angkor Express
24Eo, Ang Non (St 102), Phnom Penh; T: (023) 427 567
In front of Gasoline Station LAE, Battambang; T: (092) 575 572
#618 Tep Vong St, Siem Reap; T: (017) 525 377