what are the other suse of snake poison apart from preparation of antidote for snake bite in medical field? Is it used as a pain killer?

Yes, there are sevaral patents out for the use of snake venom as an analgesic. There are also trials on snake venom as clotting agents, anticoagulants, cancer treatments, alzheimer's treatments, analgesics for arthritis sufferers and it also has many diagnostic uses too, particularly in haematology.

 

(See here, here and here.

It's probably important to realise that there are lots of different venoms from different snakes. They have different properties and therefore different potential uses.

Well friend, In a recent article I found that venom from king cobras is being tapped to develop a new painkiller several thousand times more potent than morphine but without the addictive side-effects, and a biomedical company set up by three Singapore bodies to refine the drug and bring it to market.

Injecting increasing amounts of snake venom into one's body can increase resistance to venom from more poisonous snakes. It's a dangerous process not to be taken lightly.

From a quick google search under "uses for snake venom" as key words.

 

The use of snake venom to develop disease treatments is not a new field. Captopril, a drug used to treat high blood pressure, was derived after analyzing the venom of the South African pit viper. Aggrastat, used to treat chest pains by preventing blood clots, was developed from a peptide in the venom of an African viper.