Sucidal thoughts. College in india!

Hello doctor my husband had sucidal thoughts from last 4 years and this thoughts occur suddenly..like he is working then the thoughts come automatically..this is not the regular problem ..he had this problem last sept and recently tomorrow..according to him these things came into his mind automatically and he don't know how and why these things are came into mind..he said to me that he didn't think anything or he didn't have any issue..there is little issues in everyone life who is working there is little issue last year that is family matter like he had pressure from his mother to built house..i asked him is this his problem he said no..his job is very nice and he is also happy with his job..he was talented student also he done his bacheolar from IIT one of the reputated college in India