i hate to say it, but there's some inaccurate info here that's based on rumors or paranoia.
i've been in-country (Isaan) for over 8 years. we travel all over the country all the time. Mike South's post pretty much covers the basics. you can study that list on the plane. Bruce (adultb2b) has also been in-country a long time in Bangkok. he knows the city as well as anyone. i didn't see a post by DWB yet, but he's been in-country a long time too. tourists that visited a couple times or once a year don't know shit about Thailand. they know about tourist destinations - if that.
Malaria is not a concern. the cases are rare and you'll know if you get it. go to a clinic if you get any type of fever. most likely you wouldn't even get symptoms until you are on the way back home. it doesn't come on suddenly and you'll only be in-country a week. i don't think there were any cases of Typhoid fever breakouts last year. everyone might be thinking about Dengue. there is usually an outbreak of dengue every year during rainy season in flood areas. that's rural, swampy places. there's no dengue in BKK or CM or Krabi in May.
the much bigger concern in Thailand is belly bugs. anyone that's spent any significant time in Thailand has been stuck on the toilet at some point. the best way to avoid it is to eat carefully. if you eat street food, make sure its hot food - noodles, rice soup, boiled chicken. those sticks of pork and squid at all the street carts look delicious but they were mishandled before they were cooked and likely afterwards too. most of your sit down restaurants will be ok. just eat hot, fresh food. i got ecoli one year. that sucked. my ass leaked for a week and i spent 3 days in the hospital. i got it from eating undercooked spinach at a hiso fancy restaurant. dining is a crap shoot in Thailand. if you are worried, there's lots of Western fast food. that's not real food, so it can't carry bacteria lol
the best defense against belly bugs is whiskey. take a shot or two before bed. any bugs in your belly will be dead.
there's a 7-11 on practically every street in the country and they DO have many of the popular toiletry products from the West (colgate, axe, wine, etc). we rarely pack toiletries, even when we travel short distances. we just hit 7-11 on the way to the hotel. 7-11 also has bug spray. keep a bottle in your pocket and spray your legs and neck at dusk. you'll be fine.
the ATM advice is bs in my opinion. Siam Commercial ATMs give you the current exchange rate. they do charge a fee of 200 baht ($5), so just take out the max when you want to use them. that's usually 15-20k baht depending on your bank. carrying $500 at a time is much better than carrying your whole travel budget in your underwear. guys get ripped off all the time (taxis, bar girls, hotel maids) and then have to call home to get someone to wire them money. i always have 15-20k in my money clip and i use ATMs a couple times a week. its a good way to get the current exchange rate.
we spent a week in Aonang last March. its a fun place. the best seafood in town is near the 'port' where the longtail boats take off. the seafood place is in the little parking lot. there's a wall with about 50 tanks full of live seafood. its as fresh as it gets. we ate there every day.
the island tours pretty much suck unless you get a private tour. we were with a large group and we hit 4-5 islands a day for 2 days. the total time at each beach or dive spot was about 20-30 minutes. it was really lame. we landed on Phi Phi and had 30 minutes to eat and get back on the boat. we spent 20 minutes at that place they filmed The Beach. it was beautiful but you can't enjoy a place in 20 minutes. you are better off picking a couple destinations and hiring a boat for the day. it costs 2200 baht to get a private boat for a full day. then you can go wherever you want for as long as you want.
the nightlife in Aonang sucks. its an outdoor activity destination. everyone is asleep by 10pm. get to bed early and get up at daybreak with everyone else.
oh, the climate. we didn't have a winter this year. we had 3 cold days in December (nights in mid-60s, days around 90) and we'll have 3 days like that next week. that's the whole winter this year. spring is already here. we've seen a few spring rains in the last couple weeks. the 'tip' that hot season will start in a few months is wrong. its almost always hot. in a few weeks it will be 100+ daily and mid-April is usually the peak. its not uncommon to get 100F days any time between February and August (and usually a few others scattered throughout the year). i think its 95 today. i'll go check if i leave my air conditioned office at lunch.
May is hot but there has been some May rain in the last few years. it won't be like rainy season - which is a monsoon. the guy that said it only rains for a few hours at a time in rainy season hasn't lived in Thailand. he's thinking of Florida. it rains for a few WEEKS at a time during the 3 month rainy season. rainy season officially starts at the beginning of August and goes thru October, but it can start as early as May and end in November. if it rains in May tho, it will still be hot - just humid. if you are on a longtail boat all day in May, you'll want some cloud cover. last year it rained during Songkran (early April). that was pretty rare.
May 1st does start the low season, so prices will be pretty decent. we usually vacation in May and October every year (with a few extra vacations along the way).
the most important tip is to just be nice and smile. there's a lot of arrogant tourists that come to Thailand and think they can push their way around. Thais will ignore you, rip you off, or just treat you bad if you are an asshole. they'll go out of their way if you are nice and smiling. if there's a problem, be nice about it and it will get worked out.
there was a guy at our local bar last night who had a fight earlier in the day with an immigration officer over missing paperwork in his visa renewal. it was the expat's fault, but he got angry and lost it. he started yelling and pointing his finger at the officer. his Visa got denied and he didn't get the standard 30-day extension for fixing paperwork. today he has to travel to Laos to get a new Visa and start the process over again. he's got 3 kids, a wife, and now has to lose a few days of work. he could have just been nice and it would have worked out.
that goes the same for restaurants, hotels, shopping, etc. Thais don't care about you, and they probably don't want to be working. be nice and they'll be nice. its a laid back country. the most popular phrase in the country is Mai Pen Rai = nevermind. stressing out and getting angry won't get you what you want.
oh one last tip. search Facebook for the cities you want to hit. the major destinations all have groups of expats that either live there or travel there often. you'll get the best local advice. the Aonang/Krabi groups are really good.
