I travelled from Phnom Penh to Siam Reap by bus. Cost $6, pickup from the hotel is at 0930, bus leaves at 1000 and arrives in Siam Reap at 1545. It stops twice and you can have fried crickets or spiders for lunch if you choose, air-conditioned with narrow cramped seats, interesting journey.
Siam Reap is the place you stay at if you want to visit the vast temple complex at Angkor Wat where Laura Croft and Indiana Jones had some of their adventures, quite an amazing place.
Bus journey from Phnom Penh to Siam Reap
Angkor Night Market
Independence Garden, Killing Fields and Temple