Issues aplenty..from how legit ownership papers are to flooding issues and many more.
Belligerent neighbours might dispute your boundaries.
You will have to collect all this info from a trusted local guy..ideally a neighbour.
Better take the ownership paper to a lawyer..or your Mrs can check it's authenticity at the land office.
As many naysayers here would say, don't buy or build anything.
I lean on this option too.
Keep in mind that conflict resolution here (esp in the boonies) boils down to who has the most 'muscle'..family size...connections ..guns..etc
A lone ,ageing farang stands no chance.