Another Visa Question

Just a short one here:
Am I able to buy a 6 month visa immediately upon arrival at Siem Reap airport? If so, is it the same procedure as with 'oridinary' 30-day visa, with 2 photos & how much now? Thanks.

Nope, just get the Business/Ordinary visa (soon $35USD)rather than the Tourist visa (soon $30USD) and then get it extended with many travel agents. Long term extensions are easy, but not cheap, 6 months around $150, or 12 months for around $300. These fees MAY also be going up, who knows.
Note, that visa fees are up by $10USD as of 1 Oct. 2014.