South of the Jackal Tape, a bit before the eastern checkpoint, you'll notice a large tree reaching out over the river on the western bank. Opposite of the tree, on a rocky ledge, you can find a diamond briefcase along with a yellow plastic container of sorts. To reach the briefcase, approach the cliff from the north - you'll find a spot where you can jump onto the rocks (see smaller image). From there, follow the ledge to the east (still on the northern side of the briefcase) and you'll find some sloping rocks you can jump onto and from there gain access to the briefcase.
On the northern side of Rail Xing, down by the river, there is a briefcase on a rocky ledge. To get to it, you'll need to swim a bit to the west where you can find a small rock you can climb onto - see the smaller image in the top left corner of the screenshot; getting onto it can be a bit tricky since you'll easily slide off (try to move onto it from the east). Once you have foothold jump onto the rock to the left (west). Once there turn east (see smaller image in the lower left corner) and you can spot a narrow ledge - sprint and jump onto that. If you make it you can proceed along the ledge to the east and locate the briefcase.
Just north-west of the checkpoint near the center of the region you can find a collection of large rocks. In between them you can find a small passageway; you'll find a briefcase here sitting on some rocks.