I have a builder already, and architect (they are working on other aspects not related to the 'garage'.
I am more interested in understanding what others did when they built a self contained condo and sold it, (what issues/hurdles/rights etc) had to be worked out when the land itself wasn't being transferred.
No, as we need a garage (we bought the land for that), and the wife wants a garden for greenery, and it's behind our villa (single storey absolute ocean front), we thought instead of just the garage, as this view has to be worth a few bob, -- you can't really complain about this view--, so the idea of building a condo on top of the garage and selling it to someone made complete sense.
Note the garage is set to be 30meters back (from direct water).
So we googled 'fazwaz' and lo and behold 2 bedroom condos with sea view are 7-15m THB
So if we build it for 2m-3m (excluding the garage cost) and flog at a profit, that will offset any other costs we've accrued elsewhere (piling costs for an example), at approx 80m2 thats a nice holiday dig, with private entrance, and a few rubbles in my beer bucket.