There’s basically a couple of main ‘seasons’ for kiting in Asia, the best being the North east Monson, which is roughly December-March, and the Westerly’s which blow roughly June-September.

Hua Hin
As you will be visiting Thailand towards the very end of the NE monsoon season, Hua Hin is probably your best chance for wind. From roughly Feb through to April Hua Hin has some thermal winds (around 17-18 knots), although Windfinder won’t show anything. It’s an open beach with choppy water. Fly into Bangkok and it’s about a 4 hour drive down to Hua Hin.

Phuket
At that time of year the wind should still be blowing from the North east, in which case most people ride at Chalong Bay. Pretty flat water, a bit of chop out the back, sandy bottom with a lot of scattered rocks. Great for beginners.
Chalong can be a hassle though because it is tidal, so you can really only ride at mid to high tide, and on top of that, the wind tends to drop off during the middle the day, so getting the tide and wind to appear at the same time can be a challenge. One of the shops there (Kitezone), does some boat trips to nearby islands if the wind is blowing, and the tide is out.

Koh Samui,
During the NE Monsoon most people seem to ride at the SE corner of the island adjacent to the ‘Samui Orchid Resort’ (Just south of ‘Maret’ if you look it up on Google Earth), However, I’m sure you can ride at other spots around the island.
There’s a flat water, shallow, sandy lagoon with a reef out the back. Great for beginners. Tidal area.
FYI, flights and accom are generally more expensive than Phuket.

what about in june? koh samui alright then?