Its a version of Hare and Hounds or a paper chase.
The hare goes out in the morning and sets the trail marked with bits of paper. There will be false trails, and the trail may disappear for a bit.
In the afternoon the hounds set of to follow the course that ends up at a meeting place where lots of beer is consumed at a short meeting where names are awarded (on the second or third run), and forfeits are awarded for breaking the rules such as short-cutting.
When I used to it in Sumatra the course was about 3 - 5 miles long (5 - 8 km), and some people used to walk the course, running is only necessary at serious hash clubs.
For more info visit
www.phuket-hhh.org