Hybris code behavior in thread

Multiple things in the code is coming as null when i am trying to execute the code in separate thread. Without separate thread it's working properly. In the below code , base site id is coming as null. What could be the issue?

final CartModel cartForGuidAndSiteAndUser = getCommerceCartService().getCartForGuidAndSiteAndUser(guid,getBaseSiteService().getCurrentBaseSite(), getUserService().getCurrentUser());