In our opinion, both parties are at fault due to mis-communications. BKK only sent out the MBL on 8/7/16 which will definitely incurred charges should there any amendment on the MBL. As for MNL, they should have checked the GW on both BL and MBL when it was initially sent to them and not 1 day before manifest cut off date? Also we do not know what is the import regulations at MNL, MNL should give clear instructions before any amendments was made.
VGM have started since 1st July which all the weight declared to carrier should be total GW (Cargo + Tare), why carrier at MNL still using GW for manifest?
Due to above, I suggest both ends to split the amendment cost to settle this issue amicably.