By this letter I am applying for Leave for this coming Chinese New Year, commencing January 29th, 2006. I will return to duty on the 31st of January.
Thanks for your assistance.
Sincerely,
Etc.
NOTE:
1. I would not use "cooperation" because presumably you are asking PERMISSION. Someone in position to DECIDE about this matter will render ASSISTANCE------not COOPERATION.
2. I would NOT use "kind regards" because it connotes intimacy, which is not justified in a formal letter of this type.
Happy conjugating!