1. Gratitude and gratitude: My father may realize that he is about to die, and his gratitude may be gratitude for your company, care and support. This is his affirmation and gratitude for everything you have done.

2. Farewell and rest assured: My father may want to tell you his gratitude and concern for you. I hope you know how he felt when he died, so that you won't have any regrets in the future. He may hope that you can get comfort and strength from it and move on with your life.

3. Expression of love: At the last moment, my father may express his love for you through such gratitude. He wants you to know that no matter how things change, he loves you deeply and thanks you for your concern and love.

It should be noted that the specific context and the father's personal feelings and wishes may also affect the specific meaning of this sentence. If you can know more about your father's thoughts and feelings, or ask other family members for understanding, it may be more helpful to understand the meaning of your father's "thank you" before he died.