All the Angkor Archeological Park entrance ticket is only available at the official ticketing office which are further away from the Angkor complex itself. Inform your driver to get the ticket before proceed to complex entrance, as there is no ticketing counter at all the complex entrance. According to the ticketing office website there is no 3rd parties companies selling the ticket including at the hotels, tour company and online. The Angkor Pass also valid to visit several Angkor Archeological Park including Phnom Krom, Wat Athvea, Kbal Spean, Beng Mealea, Roluos Group and Ta Prohm Temple (temple ruins by overgrown tree). At the ticketing office you can find convenient shops selling souvenirs, clothes, snacks, bakery, smoothies, soda, tea, coffee, ATMs and many more. For more info visit https://www.siemreap.net/visit/angkor/practical/hours-admission/