I Have A Friend Who's Depressed. They Don't Seem To

I have a friend who's depressed. They don't seem to be showing any symptoms of having suicidal thoughts, but they've opened up to me in the past about a suicide attempt. As far as I know, this person hasn't ever tried to commit suicide other than once. Would he/she be more vulnerable to suicidal thoughts?
To state it simpler, would a person who had suicidal thoughts before have a greater risk of having suicidal thoughts, than a person who has not had suicidal thoughts.