to the people insisting that this isn't racist because it's supposed to prevent prostitution:

regardless of whether prostitution is a problem, the signs make the assumption that all thai people going into the guesthouse are of ill repute, which is not necessarily true.

when i traveled around by myself in china last summer, i encountered a similar attitude from the maintenance staff of hostels although there were no explicit signs. i was a single female traveler of east asian ethnicity, and i was often stopped by the staff doing things that other travelers were allowed to freely do.

for example, one night, i was coming back late with a (western) friend. the night watch guy stopped me and was very rude to me even after i told him that i was a guest and which room i was staying in. when i was leaving that hostel, they wouldn't let me get all my bags at first because they just assumed that i was stealing the valuables of westerners.

in china, they have people trying to sell those for 1-3 yuan (under 50 cents) at basically every tourist spot.

I saw BBW Wikipedia at a restaurant in Dalian this summer.

http://web.mit.edu/x_x/www/uploaded_images/CIMG0912-781329.JPG

It turned out that it was squid. Here's me with a plate of it: http://web.mit.edu/x_x/www/uploaded_images/CIMG0844-750896.JPG