Chinese visa is necessary for 2 h transit at Beijing airport (for going to USA and come back toLaos)

Dear Sir/Madam,
I am a Lao citizen and will go to USA for visiting (with US visa issued). In my air tickets to New York with Air China 980 from Bangkok, it will transit at Beijing (PEK) for about 2 hours and 40 minutes, then Air China 989 to New York. And the same way (to transit there) for coming back to Laos. So, Thank you to give me the information of Embassy of China, if it is necessary to apply for Chinese visa for these transits in the Beijing airport .