can i get a new passport in china? i am a cameroonian resident in Thailand

Isah, is there a Cameroonian embassy in Thailand? If so, you may consult with your embassy and try to apply in Thailand. If not, you may try to contact your embassy in China in advance before you go. Most importantly, you should ask the embassy how long it takes to apply. After you submit your old passport, you can't exit China until you have your new passport.