How can I interpret the hexadecimal payload:“ab006400ae” using the attached table (943.4 KB) 
Just need an example
Looks pretty straightforward, work it out with pencil and paper then if you want to use the javascript decoder copy and modify someone else’s.
So for example, the 3rd byte (eg byte #2 counting from 0) is 0x64.
Bit 7 of that is the park flag, but you can see that’s zero (otherwise the value would be larger than 0x80).
Then the battery level is the remaining 7 bits, so you could mask the value with 0x7f
eg 0x64 & 0x7f is 0x64 or 100 decimal…
Good you seem on the right track, but how do i get to the 3rd byte(how do i split the 40bit) so that i can do a bitwise operation?
While it’s true that your message can be viewed as a vector of 40 bits, it’s more traditional and in this case useful to think of it as 5 8-bit bytes.
If you are using the TTN online javascript decoder support, you’ll be handed a buffer of five bytes, so you pick the one you want and apply bitwise operations or shifts.
If you are using some other language the mechanism might be different, for example in python you might use struct.unpack_from() and in some cases in the LoRaWAN realm (if not specifically TTN) you might first need to convert a printable ASCII hex representation (for example the way things appear in your post here) to binary, or to decode base64, or similar. You could pull apart an ascii hex representation as pairs of characters first, but that’s typically something you’d do in a small test program to look at one thing, not a decoder for a full payload.