You can do better, I am building so got into Facebook and subscripted to a few building channels, I been getting add s for kitchens and solar as well as other stuff, found my solar and kitchen guy this way.
Im in the Pattaya area but building in Sattahip and will be using a 3kw system, there is no buy back of unused power in my area, the Navy runs the show there and if you stuck a bigger system on the roof id be just giving it away, and solar is purely to keep my bill low as im having a pool pump running twice a day every day.
Firstly forget the sales talk these frisbys know jacks.h.i.t one think you learn living here there product knowledge is low to non existent, and they will lie to your face for a sale, in other words tell you what you want to hear.
Had a system back in AU, 5.4kw with 10kw battery in Melbourne, battery was full by 10 am in summer, for 4 months a year I payed nothing and gained credits and the battery was sufficient in the evenings since it was just running lights and a pc. That all changes as you enter winter battery is spent in 3 to 4 hrs, cannot charge fully due to less sun etc, but the credits kept it cheap. I used a single Panasonic aircon inverter type for heating and cooling but for cooling I hardly ever turned it on.
In Thailand there is plenty of sun so battery is a good option but you will need 2 batterys if you run air con all night, they over kill here in the size they want to stick on your roof, 10kw system is double what I had back in AU, what are you running a factory? in my opinion a 5kw system will fill 2 10kw batterys in Thailands sunny weather, as I said 4 hrs of sunlight filled my 10kw battery back in AU.
My cost for a 3kw system installed will be 79,000, I suggest you shop around.
Really need more info if you want recommendations, like air cons how many and how long you run them.