Let's do a quick and dirty calculation for a simple grid-tie system that's DIY installed.
Your 2,000 Baht power bill would be about 450kWh so about 15kWh per day.
A 340W panel will give you about 1.2kWh per day so you're looking at 12 panels = 4,000W system.
Panels are around 3,400 Baht a pop = 41,000 Baht, a 4kW grid-tie inverter around 11,000 Baht. Add 10k for installation bit n bobs and you're gold for <65k.