Answer
Both systems ultimately use chlorine to control bacteria; a saltwater pool generates chlorine from dissolved salt, while a conventional system adds chlorine directly. The better choice depends on equipment quality, maintenance support, pool use, budget and the surrounding environment rather than on a claim that one system is completely chemical-free.
Salt chlorination can provide steady sanitation and may feel gentler to some swimmers, but the generator cell needs cleaning and eventual replacement. Salt can also accelerate corrosion if unsuitable metals, fixings or nearby finishes are exposed. Conventional dosing is simpler and familiar to many technicians, but water chemistry must be monitored consistently and chemical storage handled safely.
In Phuket, heavy rain and warm temperatures can change water balance quickly whichever system is used. Correct filtration, circulation, drainage and routine testing matter more than the label. Ask a local pool professional to size the equipment for the actual water volume and usage, and compare lifetime maintenance costs rather than only the initial installation price.