It appears to me that you are wondering why you have thoughts about dying when you are not depressed and are happy in general.
You might have to describe your thoughts about dying in more details -
1) Do these thoughts intrude into your mind even when you don;t want them?
2) Since when do you have this problem?
3) Have you ever been diagnosed with Depression
, or had similar thoughts in the past?
4) What are the exact thoughts? Do you visualize or imagine how you will die or attempt self harm?
If you do not have symptoms such as sadness of mood, loss of interest, sleep disturbances, irritability, etc., you may not be depressed.
Abhijeet Deshmukh, MD