Actually the rainy season varies from micro-region to micro-region. Here are a couple general breakdowns:
Thailand weather
What’s the weather like in Thailand?
…and my favorite resource:
Thailand interactive weather information
I went to Koh’s Samui, Phang-an & Tao in September and the weather was fabulous. An hour’s worth of afternoon downpour per day, that was it. The real raining doesn’t kick in in that area 'til October, from what I hear.
However, I’m not a fan of the whole Gulf of Thailand island scene. Touristy. Crappy diving. Even crappier snorkeling. And the beaches just aren’t as beautiful.
Although there is greater differential between rainy and dry seasons on the Andaman coast, I have heard from a couple Farang (Westerner) residents living in Trang that actually even there the rainy season is quite comfortable - just afternoon showers, much as in Taiwan.
Without making any promises in that regard - I’ve never actually been there outside of February and March - I will make the following recommendation - provided you exhort your wife not to pass this info on to any Taiwanese! (One thing I LOVE about Trang is not hearing a WORD of Chinese there!) Anyway, the location I’m referring to is Koh Hai in Trang. Both of the following resorts there are nice:
Koh Hai Resort
Koh Hai Fantasy Resort
Both places have nice pleasant-looking and comfortable bungalows and pools for the kiddies. No trash on the beach and no frickin’ full moon parties. Fantasy resort is actually the more beautiful of the two (the view from the beach is the best of any resort in Thailand - I’d be willing to put money on it), but it’s also pricier and not quite as social if you like the whole hippy traveler scene.
Getting there is easy. Catch a morning flight to Bangkok. Afternoon domestic flightfrom Don Mueng airport to Trang town on Nok Air takes about 1.5 hours. Book your boat trip (and hotel, if you haven’t already) for the next day at one of the many little travel agencies by Trang train station. Spend one night in Trang. Hit the Trang hotel for a cheap massage and maybe check out the night market. Catch a mini-bus to Pak Meng Pier mid-morning from Trang town train station. An hour’s boat ride, and you’re in paradise!
As for a run-down of all the places I’ve been to… I’ll try to work on it later.