Dear Kannansai,
Good to note that you have completed three years in your current company. Nevertheless, if you send a thank you note to your colleagues for giving you support, then you could be going overboard. Placing the compliments on records is uncalled for.
You could complete three years not just because of your colleagues but also because of your capability. A complete credit cannot be transferred to your reporting manager and colleagues for a successful stint of three years. Completing 'X' number of years in a company need not be a matter of celebration. Yes, if you get some reward like "Best Employee of the Month", you may give credit to your manager and colleagues. But that also needs to be done when the actual award is given at that time. No need to send a written note.
Please note that life is non-linear. How you spent the last three years, exactly in the same fashion you may not spend time in future. Therefore, take it lightly. Unless there is a custom in your office to celebrate the anniversary of joining, no need to do anything. In case if you are working from the office, and not home, then to express your gratefulness, give some chocolate or something and move on.
Thanks,
Dinesh Divekar