This is a public health issue.
If what follows is already mentioned by a poster then so be it as I have not trawled through all the replies.
However I was recently asked by an acquaintance here in Thailand as to what remedy to use for body lice and I made some enquiries and did some research.
Also with the lifestyle of many and the ignorance of others plus the fact that massage establishments etc are potential if not actual breeding grounds for the lice there is always the risk of widespread infection.
An early poster suggested using "Jacutin" Gel.
That is now banned in Thailand and the reasons for that can be found from a google search.
The lotion now available in many Pharmacies is called:
"Hexin Lice Killer Cream".
It is available in most pharmacies and retails for 20-30 baht.
One application overnight for 12 hours is said to be sufficient.