Check out Nomadic Matt’s article titled How To Pack A Professional Travel First Aid Kit.
This is an excellent article on what kind of first aid supplies you should carry when traveling. For most folks, Matt’s list would be enough to treat the majority of injuries they might encounter.
I would add a few things to make it more complete:
– a CAT Tourniquet for severe bleeding
– some duct tape (because surgical tape doesn’t stick well to wet skin)
– a broad spectrum antibiotic (usually Cipro, Levaquin, or Augmentin but you may consider Azithromycin if traveling in SE Asia)
– a prescription anti-nausea medication like Zofran.
Depending upon where you travel, you may be able to buy the prescription meds I recommend over the counter in other countries.