Secondly, you will need a fair sized pump to get enough pressure and flow to cover an arc of 12 metres. To reduce the friction losses in the piping it is important to have a large diameter supply line, or "ring main". At least 1.5 inch PVC. The tee off to sprinklers can be much smaller, providing that it is just a short distance.
Brass "impact" sprinklers that have an adjustable arc are readily available at around 400 bht each, or there are similar plastic body types a bit cheaper.
Or you could use "pop-up" sprinklers run out from your wall in "zones" without disturbing the existing lawn too much. There is a multitude of different types of sprinklers available, and all the fittings required to connect them. It is very easy to install using "PE" piping.
The biggest problem, apart from the cost, is finding somebody to do it. I will put a link here and hope that it is allowed. They have a young bloke, I think he is part of the family, that speaks good English and will do a design for you if you give him a plan of your garden. If you are in Bangkok you could pick up a catalogue at the Phaholyothin shop that is right opposite the "Elephant" building, which has all the products, plus the technical info for calculating flow rates and pipe losses.
http://www.superproducts.co.th/index.html
