It depends on what type of annuity it is and if the account has an RMD withdrawal requirement.
If you have a retirement account like a pension, then those monthly payments are not RMD's
If you have a retirement account that is funded with after tax money like a ROTH IRA and you are the owner (not an inherited account) you do not have a RMD requirement.
If it was any type employer sponsored retirement account, like a 401k, and you are taking monthly payments, then yes, that can count as your RMD. As long as you withdrawal the minimum required amount throughout the year, it doesn't matter if it is monthly or in one lump sum.