You can fly, take the bus or take a boat. The bus is definitely cheaper (around $10 one way), more comfortable and more scenic than the boat. Bus and boats both take roughly the same amount of time (6 hours), but the boats take longer in the dry season. If you choose to fly, you can fly with Bangkok airlines for about $90 one way and it'll only take 30 minutes. If you're not on a budget, I'd say flying is best from Phnom Penh to Angkor Wat
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