The Preferred Hash Hotel is the Thavisouk Hotel by Nam Song River.
Address: Ban Muangsong, Vang Vieng, Laos

To get a special Hash Discount, book this hotel thru Chris Tan.
Send Chris a Whatsapp message to make the booking (+60 12 223 1111)

First, you will have to be registered with SHOT to book a room.
There are 30 rooms blocked booked and its on a 1st come basis. 

Room bookings to be paid to Yoong Nim Chee
Price :  USD 40 before 30 July 2017
           USD 55 after July 2017

Photo from the hotel shown below. Link to some photos here