i have a koi pond now and the waters going green i would like to buy a uv light for the pond, but i live in angthong thailand can anybody help me as to were i can buy

If./when you are in Bangkok, go to Chatujak Market. The backside, near JJ Mall, has a huge pet and fish supply area. It also runs down the full length of the street that goes behind JJ Mall and runs down to the park where the Sky Train Station is located. There are at least 20 sellers, some inside the market and some on the street, so it pays to shop for a few minutes before buying. I get mine there (as well as all other koi pond supplies and occasionally fish) for about B1200. The bulbs last for about 1 year and then need to be replaced, so you might want to pick up a replacement bulb when you buy the light (around B550).