Sak krub,
I would like to flow OPT-Services JOB (collect money track) this way krub.
Fah issue PO, 1 copy will go to Su.
When your team complete, pls issue us a CERTIFICATE (detail or not detail depend on your JOB).
Once done, pls return the certificate to Fah.
Fah close PO-->Delivery to Aonn.
Aonn deliver with Invoice.