Visas are required to enter Cambodia. You may get a visa in advance at your nearest Cambodian embassy or obtain visa upon arrival at Siem Reap Airport, Pochentong Airport in Phnom Penh, Aranya Prathet-Poipet border, Trat-Koh Kong border, and Moc Bai-Bavet border. One passport-sized photo, a photocopy of passport valid for at least 6 months, and USD 20 are required. Cambodia visa is valid for 30 days from the date of issuance. You can also extend your visa at the Department of Immigration, located opposite of Phnom Penh airport.