Flat water and consistent wind
Winter season (November — March)
Many islands in Philippines like:
— Boracay, real flat on low tide (2 hours a day), now its from 6am to 8am. If you can wake up early, that is for you. Wide choice of accommodation. Good kitesurfing infrastructure. No-wind attractions. Good for going with girlfriend — nice beaches. Overprices and overcrowded. Most developed and easy-going kitesurfing destination in Asia.
— Daet / Bagasbas. I've hear, that it's not crowded, more wild, more wind, less sunny.
— Many other islands (like Cuyo) with reef protected lagoons, but in other things they are overall wild destinations.
— Phu Qyu. Small and "wild", island in the middle of sea, wind is nuking like hell, waves up to 3-4m. No infrastructure, no internet, serious problems with electricity. If there is big waves (which is quite often), ferry stops to go, so you're stuck for 1,2,3,4 weeks (who knows?).
— Cam Ranh. Far from accommodation, lake, no infrastructure, no kiters, wind is gusty (due to mountains).
China / Hainan. Don't know much about this spot.
Summer season (May — September)
— Kalpitiya, going there in 1 month. Very big lagoons with flat water, wind should be consistent due to Venturi effect, very wild, almost no infrastructure.
All year round destination
— Penghu islands. Wind is nuking (too much very often), all year round destination (again Venturi). Some spots with flat water. Not very warm there.
Flat water because of no wind
— Bali. Sometimes you can get some wind for 12m².
— Thailand (all spots). Sometimes you can get even for 9m² kite, but most of the time you're sitting on the beach and waiting for a miracle. You can have kiteboarding as a bonus, but going for only kiting there would be frustrating experience. Nice infrastructure in some spots (Hua Hin) — big choice and low prices for accommodation, wide beach, lots of shops and schools.