Swimming pools are fun...

A great way to keep cool in Isaan
Local contractors will build you one for 1 million baht or more. Less expensive alternatives are available.

Things to consider:

Size

Do you really need an olympic size swimming pool?
Large pools require more maintenance and are more expensive to operate.
They also tend to attract more visitors.
If small children are going to use the pool, considering the depth is also important.
Above ground or below ground pool. Below ground pools will require pumping to drain a pool.

Water supply.

Pool water should be changed once or twice a year, depending greatly on usage and maintenance.
Having water trucked in is the most expensive way of filling your pool.
If you're using ground water you may be confronted with undesirable additives requiring extra filtration.
My personal preference was the installation of a number of large water tanks which store rain water.
Local tropical rains are heavy enough to fill your pool in under an hour.

Shower and toilet facilities

A must, unless you want all your visitors traipsing through your house.

Pool supplies

Pumps, filters, chemicals can be acquired locally, but of course are more costly than getting them from a pool supplier in Bangkok.
There are a variety of pumps and filters, get some professional advice. Visit a pool shop in Bangkok

The amount of chemicals required depends on the size of the pool and the cleanliness of the users.
I tell my guest to shower before and after using the pool.
Unfortunately their understanding of taking a shower means simply getting wet.
Body sweat, oils, makeup perfumes, colognes, hair gel, all will require extra pool cleaning.

Covered or uncovered

Open pools tend to collect more dust, leaves and other debris, while enclosed pools will have less of this problem.

Lightening

Great for evening pool parties, but they also tend to attract a large number of uninvited guests: bugs.
Yellow fluorescent lighting seems to attract the least number of bugs, white or black-light attracts the most.

Tile or cement

I made the mistake of tiling the floor around the pool. The kids had a ball using the wet floor as a slide.
But after a third fall, causing injury, that was replaced.

First mistake: Too small. I wanted something more like a jacuzzi.

Second Mistake: Started digging during the rainy season.

* Neighborhood teens provided inexpensive labor.
Planned the depth to be even with street water drains. Pool can be emptied without pumps.

With a roof to protect from the elements, a local contractor poured the cement.