Exactly BB. They see the neighbor succeed so they try to copy them. The thing is, the neighbor might have loads of contacts in the area which support him or her. If the new start up succeeds, then another is sure to follow, and another, and another. personally, it would reall piss me off if i started something, and tomorrow everyone else in the soi is copying me. Nonetheless, the Thais don't seem to mind.
A short while ago a place opened, that was originally going to be a restaurant, just down the road from us, and just meters from a very successful Mom and Pop shop. If it had been you and I, we would more than likely have struck a deal.........you have the shop; I have the restaurant. If your customers want to eat, you recommend my restaurant, which of course uses your shop for all refreshments and etc. In this case however, the two places have gone totally against each other. In fact, they are now enemies.
You really don't need, at least in my opinion, a degree to work out the whole "saturation" thing. Why open a laundry in a very small soi where there are already 10 laundries? We also don't need another car wash or another shop.

How about a massage place where the women are below the age of 50?

Maybe a Farang style bakery, considering that the area is full of Farange? Maybe not a viable idea for a Farang but a Thai could cash in if they were willing to learn and/or adapt.

Don't try to impress me with your manner of dress cos a monkey himself is a monkey no less - cold fact