You need backup batteries to store the solar generated electric power for blackout at night or days without enough sunshine. During a longer period rainy-season your will be without power or without backup.
I've been living permanently on Samui for 18 years now – came here for a littler longer period – the power cuts are luckily much less now than before. If you have weekly blackout it might rather be too much load on the local transformer or a too small cable somewhere in the grid; we had that problem, PEA replaced it with a bigger transformer and larger cables...????
When I designed my house to be build, I included a backup power-system based on simple UPS units and a larger battery and inverter for the most necessary light.
Be aware of water pump and the type of inverter used. I made my house with a tank on the attic instead, so I always have running tap-water. You can also use a 12-volt water pump, but they are rather expensive.
My design was a number of UPS to power computer(s), screen(s), TVs and other sensitive electronics, which also protects the electronics from variations in the main supply. Furthermore I have a separate cable-network for "emergency" lighting, so there always are light in bathroom – the unwanted situation washing hair and power cut at the moment the soap run into the eyes during both blackout and no water... – kitchen, stairs, some outside lamps etc. It's powered by a larger battery and an inverter, and charged from the mains, so it also works during the rainy season. With LED lighting a battery can easily give enough time for a reasonable black out – like 5-6 hours or more – before main power is restored.
Using mains-charged battery pack and inverter(s) for important stuff only, might be a more solid – and cheaper – solution for Samui, than solar power, which also won't work during rainy season.