I copied the following from a thread I saved on wakeboarder.com at least a year ago, so the information may be out of date.
CABLE SKIS
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Bang Na - Taco Lake - 300 Baht/2 hours ($7)
Pattya - Lake Land - 300 Baht/2 hours ($7)
Ratchaburi - Lake Point - 100 Baht/hour ($2.50)
Phuket - Khatu Waterfall -600 Baht/2 hours ($14) (cheaper for Thai's)
Schools
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Pattya - Air time - 700Baht/15 minutes ($16.50)
www.air-time.net Phuket - Wake-up Villa - 700Baht/15 minutes ($16.50)
http://www.wakeupvilla.com/link.html