Hi Huy
It might be a litlle too late to answer your question, but maybe, it will be helpful any way.
Incoming and outgoing payments are handled in FT module in T24. Also in T24 you can find TWS module to create web services and be able to consume that service to push payments from SAP PE to T24.
You might need some help from a T24 consultant to map all relevand data and crete a message.
Cheers