This video shows you how to jump across the river Ganges in the level of the same name after following the left path. (And how to get the ammo on the ledge here.)

This way you can collect all the goodies by first doing the left path and then doing the right path (with the monkey temple) backwards and on foot.

You can also obtain the trophy Monkey Temple this way, if you jump back across the river and finish the level even if you never took the quad bike along the right path, and even when you killed all monkeys with your guns.

How to align the jump (classic aka tank controls):
Walk up to the water's edge and sidestep until you hit the left wall, then turn to the left to face into the corner.
Hop back to get a run-up.
Run ahead, press jump.
While in the air steer slightly left.

Now there are two methods. I found the 2nd one more reliant, but I recorded both for you.
Method 1: Do not press action to grab the ledge. (Lara might still fall off the ledge)
Method 2: Press action to grab the ledge.


NOTE:
To get back across the river here, make a running jump onto the familiar tree root again. Turn slightly to the left and make a running jump onto the long ledge on the left wall. Now comes the most difficult jump of the whole trip. The idea is to take a curved jump from this platform around the cliff wall back onto the large platform above the slop. Hang onto the ledge opposite the rock face and shimmy first to the far left and then once to the right. Pull up and turn so that Lara is facing slightly left past the corner. If you can save freely, do so! Now run forwards and jump off in the corner, counter-steer in the air to the right to hopefully land in the corner of the platform behind the wall. In the remastered version, I only managed this jump with the ‘modern controls’ (gamepad), because Lara is pushed off the wall when she jumps upon reaching the corner. Switch to this mode before the jump, start running, jump off, pull the stick to the right in the air and hopefully land correctly. On PlayStation, remember that jumping is now X and forget for a moment that it's Classic Tomb Raider.
(I will edit and upload the video showing you how tomorrow.)