En route to China,visiting Africa, India, beforeThailand,Laos,Cambodia,can I apply in either country

China visa is valid for 30 month in general. SO, if your travel to other countries is less than 3 month before entering China, you can apply for China visa in your home country. Otherwise, you need to try to apply in other country you are travelling. Anyway, it is easy for you to get a visa in your home country than others.