I am a Filipino. My friend is Saudi man. He wants to meet me in hongkong. I have my one way ticket

Even if there is no need for visa to Hongkong for Filipino passport holder, you are required to have a return ticket to be shown at the immigration. You are most likely be questioned and not be allowed departure or if allowed here in Philippines, you wont be allowed entry. Hongkong immigration will most probably assume you are going to Hongkong other than being a tourist. Getting a work or staying more than 14 days in Hongkong will already require Visa.