Is it permissible to continue working and having lunch with people who use foul language and curse religion and political figures, knowing that I do not participate in their conversations but sometimes laugh at some of their jokes?

What these people are doing is forbidden backbiting, and it may even reach the point of wrongly declaring a Muslim an unbeliever, which is a grave evil. So do not sit with them while they are committing this evil, unless you admonish them. Otherwise, do not sit with them, especially if you laugh with them, as that would be your approval. Explain to them wisely that you will not sit with them while they are committing this evil. The Messenger of Allah, peace and blessings be upon him, said: "Whoever pleases people by displeasing Allah, Allah will abandon him to the people. And whoever displeases people by pleasing Allah, Allah will suffice him against the burden of the people."