Before you bring up the subject, you can follow all the tips in the section Engage with your friend.
It is often difficult to ask someone if they are thinking about suicide: it is normal to have fears because it is not an easy subject to discuss.
First of all, you should know that asking a loved one if they are thinking about committing suicide will not provoke it, whether or not they are having suicidal thoughts.
Find a quiet place to talk and really listen to your friend with empathy. If you want to ask your friend if they are having suicidal thoughts, you need to make this clear and explicit. Only ask the question if you feel comfortable, ready to receive the answer and have time afterwards to be available for your friend.
Have you been having suicidal thoughts lately?
Have you ever considered killing yourself?
Are you thinking about suicide?
Asking them if they are thinking of committing suicide can show them that you are ready to talk about this subject with them, to speak up, to bring them relief and to have a clear and precise answer to react in the most adapted way.