Dear Mr. XYZ,
I would like to thank you sincerely for your all support and help
during my employment with your organisation. Thank you for the
experience you have afforded me and for your confidence in assigning me to a high-level position, which will serve me in good stead in attaining success in my career.
I am very grateful for all you have done for me.
Yours sincerely,
Harpreet Singh