North-west of the Weapons Shop, past the railroad, you'll come upon a small pond or body of water. At the northern side sits a large rock - behind the rock is a briefcase.
Just south of the road going from the Weapons Shop to a checkpoint near the center of the region you'll find a safehouse. A few paces north of it you can find a diamond briefcase inside a small shack.
In the south-eastern part of the region you can find a small shantytown near the river. A briefcase is sitting on a bed inside a shack at the north-eastern side.
In the southern part of the region you'll find a checkpoint north of a bridge. A briefcase is located beneath the bridge on the southern side; you should be able to spot it if you move to the eastern side of the bridge (see screenshot).
A road connects a checkpoint near the center with a checkpoint in the southern part of the region. Along the road you'll come upon a couple of shacks - a diamond briefcase is located on one of the roofs. You should be able to spot it straight away. Getting to it, however, is not as simple; next to the shack you'll find a trashed car which may be able to get you high enough to jump onto the roof. A more solid approach is jumping onto the burned out truck at the back and using that to jump onto the smaller part of the roof, and then onto the main roof.
Just off the road north of Shwasana you'll find an old, trashed bus. The briefcase here is located on the roof of the bus. To get to it, jump onto the front of the bus and from there onto the roof.
If you follow the road going south-west towards Shwasana you'll quickly come to a small wooden plateau resembling a looking point or somesuch. Moving there you'll be able to spot a trashed car nearby. Next to the car is a briefcase.