The alley is now the entrance to Strand Residences parking. The Art Space is on the north side of the entrance. So your conclusion is basically correct except that the parking entrance (the old alley) is between the Strand and the Art Space.

Thing Lor Art Space is a short distance up Soi 55, next to Strand Residences. Sit and Wonder is shown at 3 different locations on open street map. Only one is correct and that one is on Soi 57. The 2 locations on Soi 55 are wrong.

I added this location awhile ago so I am not sure. However, I am in Bsngkok and will be in that neighborhood, so I will check it out again in a few days.