After talking to you that account always send the invoice separate from monthly report, I think it is a OK but you should have copy of transmittal letter of the monthly report send it along with the invoicing.
So basically, the monthly report must finish by the 25th of each month for all projects, so we will not have payments issue.
Please PMC site manger please finish monthly report ASAP, please get the example of monthly report from the old report from Khun Narong and or Khun Navakul.
Please contact me via email if you have any problem working on monthly report by 25th of each month, please plan your work accordingly.