One reason Soi Suan Son may be haunted is that most of the buildings do not have spirit houses. Without a spirit house, spirits are left to roam around causing mischief. Siam School used to have a spirit house, but the owners are Mormon and took it away. Spirit houses must be built by special spirt house artisans, or spirits just won't live there. I'm not sure of the circumstances under which a spirit house would need to be replaced, but it does happen. Old spirit houses can't just be tossed out; they are usually left near a sacred tree.
This is part of a spirit house cemetery near the Tesco Lotus grocery store.
Of course the Tesco has an elaborate, active spirit house with plenty of water and incense and the occasional sandwich for the spirits.
More transient businesses, though, like the stalls at the market, can't very well build spirit houses. Instead they place an offering of red Fanta with a straw in it on the corner of their table. Overwhelmingly, the spirits at restaurants and food stalls prefer red Fanta. Oui, a fellow who works at Christie's, says that they would never leave an offering of Coke, but only red or green Fanta. I'm not sure if it's because the spirits don't like caffeine, or that they like pretty colors. He seemed to think these were silly questions.
But when I do drink red Fanta now, I kind of like to know that it's the beverage of choice for the spirits.