I married a Thai woman from Baan Khok Kong, Nong Bua Ban, Rattanaburi District, Surin in the summer of 2019 in the USA. We will be living 6 months a year in the USA, and perhaps 3-4 months a year in Thailand.
We have begun building a house on her land, and the first thing we did was have a well drilled in November 2019. I'm sharing our experience in case it helps others. I had difficulty finding good information about well drilling.
First, here is what I discovered about the hydrology of Surin. Surin is a big flat sedimentary plain well-suited to growing one crop of rice a year. As there is little irrigation water available, no commercial crops are grown in the hot dry season from December to June. The soil is red clay. Salinity buildup in the soil due to fertilizer is a problem, compounded by the presence of rock salt layers in the soil.
Underlying the clay deep down are layer(s) of gravel, starting at 30-35 meters deep or so. Before the upper clay sediment was deposited, field termites removed the sand grains from the gravel while working, leaving a porous layer. This is where you will find water.
We hired a local well driller who says he is 'the best in Surin'. He quoted 22,000 THB to drill a well up to 50 meters deep, including the upper casing, but not the pump or pipes.
He promptly drove up in a mid-size pickup with rustic drilling rig mounted in back. A small pool was dug nearby, and filled with water from a neighbor. The drilling tower was tipped up, and a carbide-tipped drill of about 20cm diameter was mounted. Drilling commenced by hand-crank starting the small diesel engine. A powerful stream of water forced through the drilling pipe flushed out the drilled dirt into the pond, where it settled. The pond served as a recirculating water supply.
3 meter pipe sections were added periodically. After going down about 12 meters, a 20cm PVC pipe was forced down the hole as a sleeve. Then a 10mm bit was inserted into the casing, and drilling continued. The hole from here on down was not cased. I hope this is sufficient casing to keep out surface water!
Around 35m deep, lots of small gravel began appearing in the upwelling water. The drillers stopped for the evening. Drilling continued the next morning to 40-45 meters. The well driller recommended not going any further, as in his experience, there was danger of hitting very salty water. So we stopped drilling, and the following day purchased a submersible pump at an agricultural supply store in nearby Rattanaburi. An American-made pump (Schaefer Legend by Ferguson) was recommended as more durable than the less expensive Chinese versions. In our case, at 40 meters deep, we were told that a 1 HP model was appropriate. The pump, pipe and supplies cost 16,000 THB. It includes a control box up in the pump house, where the starter capacitor is housed, so you can replace it without pulling the pump.
The well driller installed the pump at no extra charge, and started it up. It appears so far that our well can yield 5-6 liters per minute if pumping steadily, at least in the dry season. It could be more, we're still testing. Pump faster, and you can draw it down below the pump. As our 1 HP pump will pump 100 liters per minute, it would seem that a smaller pump would have been quite adequate. Oh, well. A smaller pump would use less electricity, but it's too late now. We're not a farm, and will just have 3 bedrooms and a small garden. This pump draws about 7 amps.
We will pump water up into a 1,050 liter tank at ground level, and then using a small automatic constant pressure pump to supply the house from the tank. We are storing grey water separately for irrigation, so one or two tankfuls a day should be plenty. We'll build a small pump house around the tank and house pump.
As they used detergent to clean out the well post-drilling, I have not tasted the water, so I have no idea if it is brackish (salty) yet. I probably will have a sample tested. I doubt that we'll use it as drinking water.
All in all, I'm glad to have a reliable independent source of water in Surin, and found the well driller competent and cost-effective. Is it cost-effective overall vs. buying water from the village? I don't know yet. I'll be happy to answer inquiries.