You can buy kratom on Lazada. It comes in powder or leaf form, quite inexpensive.
As I understand my supplier's process, it consists of macerating 100 leaves, and extracting the kratom by boiling in 6 litres of water. Refrigerate after cooling. Shake well.
I take a modest dose, half a cup. YMMV. I find it works best on an empty stomach, although I do have a bit of mango or pineapple to offset the bitter taste.
Normally, when I play golf, I have moderate hip, quad, and back pain. Kratom enables freedom of movement without pain.
As I understand it, synthetic opiates such as tramadol, oxycodone and morphine block specific pain receptors, whereas kratom blocks them all.
Good luck.