I have bought a fairly old house in central South Africa. The outer wall have sandstone block foundations and appear very stable. The floors are concrete, not cracked and generally level. However, several of the inner deviding walls are cracked with the craks opening and closing in time with the rainy & dry seasons. If filled when open they bulge out when closed! As the structural integrity of the building does not seem to be affected I see the problem as cosmetic and most easily solved by installing panelling or dry wall to hide the cracks. However, I would welcome any other suggestions.
I detect a very urgent need to conduct an on-site investigation that to be thorough will need to be of at least three weeks duration plus a further week to write a most detailed report. My rates are very reasonable and a return air ticket in the post to my home address ensures very prompt attention.
Seriously though, its very difficult to advise you. Your soil conditions when coupled with local building regs and standards are not likely to be like snything experienced up here in the Northern Hemisphere.
If it were me I'd be looking at hiring the services of a structural engineer with local knowledge to advise me on the fabric of the building before I even thought about covering these cracks up let alone the method of so doing.