From our discussion about trade agreement between Parisien and CFF, I would like to conclude the proposal as following.
1. Invoice 1-15 M CFF account place invoice via e-mail on 16 M Customer paid 25 M (transfer to CFF bank account)
2. Invoice 16-31M CFF account place invoice via e-mail on 1 M+1 Customer paid 10 M+1(transfer to CFF bank account)
It seems the actual TO be far from the amount that you told me (around 100 KB/month) so that CFF propose the special discount 1% only.
TO every 15 days Trade discount
TO 1-100000 1.00%
TO 100,001-500,000 1.50%
TO >500,001 THB 2.00%
Here below is an example for the 1st payment.