Singha Beer is served everywhere, and you can also get other Thai brands like Leo and Chang. There's a good strong German beer called Kloster, or you can drink the more expensive imports, Carlsberg and Heineken. 

Food & Drink Golden Rules

1. Don't drink the tap water.  The Thais don't.  Safe bottled drinking water and potable ice are available in all restaurants, bars, supermarkets, and hotels.  Drink plenty of water.

2. Eat in places where other people are eating:  popular restaurants and cafes have a quick turnover, which should mean the food is really fresh.

3. Take it easy with the highly spiced stuff until you've got used to it, but try something new every day.

4. For your main meal of the day, try to eat Thai-style:  order one dish per person and one for luck, and try to order different things:  one soup dish, one curry, one seafood dish, one stir-fry, one salad, and so on.  Plonk all of these down in the middle of the table so that everyone can try a bit of everything.  Don't expect soups or starters to turn up first, because the Thais don't break meals up this way.  The food all arrives when it's ready, and you start eating when the first dish arrives.

Generally

The Thais don't like their food to be flavoured too subtly.  Their spicy dishes tend to be very spicy, their sour dishes tend to be very sour, and their sweet dishes tend to be very sweet.  For your main meal, you'll be given a spoon and a fork, and the idea is to push food onto the spoon with the fork.  You will only be served with chop sticks when you order noodle soup. (I am not making this up). 

When you're dining Thai-style among friends, it's considered polite to help yourself to rice first, then add a spoonful or two of one of the main dishes to your plate.  You should eat this first before moving on to another dish.  Piling everything on your plate all at once is very rude.  If you're sharing food with Thais, they'll often put food on your plate from the communal dishes, and it's polite not to refuse it even if you're stuffed to the gills.  The way around this is simply to say thanks, and then leave most of it on your plate.  They'll soon get the message that you've had your fill.

Rice is the staple carbohydrate, and you can think of most Thai meat and vegetable dishes as being different ways of flavouring your rice.  The classic Thai fragrant steamed rice (khao soway) will be served on a plate or in a small bowl, so that you can spoon other dishes on to it.  You will also encounter fried rice and rice soup, which are both good for breakfast.  Sticky rice (khao nee-ow) is popular in the north and north-east, and is served in a little basket.  You take a little in your right hand and roll it into a ball.  You then dip the ball into a dish of your choice and pop it into your mouth.

Noodles come in a number of varieties (egg noodles, rice noodles, glass noodles), and are eaten either in soup, or in stir fries, in salads, or with thin curry poured over (called khanom jeen).  Noodle soup (gway-tee-ow nam) is great for breakfast.

Meat is eaten by most Thais, generally in small quantities with stir-fries and in salads and curries.  You won't find lamb in Thai or Chinese cooking, but thin strips of chicken, pork or beef feature in many recipes.  You won't see steaks or chops or joints of meat unless you eat in a Western-style restaurant catering for Westerners.  If you don't fancy eating in those kind of places - and I don't - you can still get a decent mouthful of meat from a foodstall selling grilled or deep fried chicken, or sausages, or little satay sticks with pork, beef or chicken. 

Seafood is cheap and readily-available in Bangkok and on the long peninsular coast down south.  You can get sea bass, silver pomfrets, snappers, huge prawns, lobsters, crabs, squid, baby clams, oysters, green-lipped mussels, and just about anything else you fancy.

Vegetables are also plentiful and cheap, and will usually come stir-fried and laced with garlic in a gravy made with oyster sauce, fish sauce and/or soy sauce. 

Strict vegetarians and other fussy eaters (apologies, Chris) may miss out on the best of Thai food, and few Thais that I've met are vegetarians.  Pong says fish sauce (nam pla) is impossible to avoid.  It's a thin light brown liquid made from fermented anchovies, and it's used where salt would be used in the west.  It's as essential to Thai cuisine as olive oil is to the Italians.  Your dishes will already include some, and there will be a bottle or bowl of it on the table if you want to add more seasoning.  It's mixed with lime juice, chillis and garlic to make a ferociously hot dipping sauce for seafood called prik nam pla.  The Thais also use shrimp paste in their curries and little dried shrimps in dishes like pad Thai (stir-fried noodles).  Stir-fried mixed vegetables (pak pad ruam mit) with almost certainly come with a gravy including fish sauce and/or oyster sauce.

Fruits are available everywhere, and they are also cheap.  You'll see a bewildering array of things you've never seen before, so try some.  Crunchy green mangoes (ma-muang), mangosteens (man-gut), longans (lamyai), rambutans, papayas,  and durians are seasonally available in most markets.

Chang Beer

Leo Beer

Bia Chang

Bia Lee-oh

Where to eat

Foodstalls: These little mobile trolleys get set up in night markets (talaart yen) and on street corners, and each one will usually prepare one type of food only.  Some will specialise in fried rice and noodles, some in deep fried or barbecued chicken or seafood, some in curries, some in drinks, and some in fruit.  You just find a table nearby, and order what you want from as many stalls as you want.  You pay the nearest cook, and the cook sorts out what you owe the other stalls.  There's no territoriality involved.  Very cheap, and tipping is not expected.

Noodle Shops: You'll see these everywhere.  They're identified by a little glass cabinet at the front of the shop displaying a selection of fresh noodles, vegetables, and meat - usually crispy pork bellies, barbecued pork, or little fish balls.  They specialise in noodle soups.  If you have trouble with the language, just point at the things you want added to your soup.  One of my favourites is egg noodle soup with barbecued pork - ba-mee nam moo-daeng.  Again, very cheap, and tipping is not expected.  

Curry Shops: You'll see trays or pots of rich looking red, green and yellow curries in cabinets at the front of these.  You're usually welcome to give the pots a stir with a spoon to try and work out what's inside.  Order what you fancy over a plate of steamed rice.  Thai green curry (gaeng khiow waarn) has achieved cult status in the UK as a classic dish, but I prefer the southern muslim-style curries which are red and called gaeng mussaman or gaeng pinang.  Cheap - no tip expected.

Restaurants: These come in all shapes, sizes and price-brackets.  Choose one that's got a good number of Thai customers, and you're unlikely to be disappointed.  Sometimes, the menus are only in Thai script.  Don't be put off - the trick is to learn the names of some classic or favourite Thai dishes, and just ask for these.  The restaurant will usually cope with your mis-pronunciation.  Eventually.

Bars: Bars aimed at westerners will either not serve food - so-called "bar-beers" - or will have an extensive menu of western and toned-down Thai food.  Don't be surprised to see "brattwurst mit brott", sauerkraut and pizza alongside tom yam goong on the menu in these places.  I don't know about you, but my heart sinks when I see a chalk board outside a bar offering roast beef and yorkshire pud.  Bars catering for mainly Thai customers will always serve food.  The Thais don't seem to go out for a beer or whisky session without also ordering loads of food.

Ba-mee nam moo-daeng

Tom yam goong

Gaeng pet jay

These are only a tiny selection of the dishes available.  I've seen some extraordinary food served up and wolfed down by Thai friends, including live prawns (goong ten - or "dancing prawns") still jumping around having been doused with garlic, chilli, lime juice and fish sauce, as well as huge deep fried insects on sticks, crispy beetles, horse-shoe crabs (like something out of Alien), and scalded cockles which look for all the world as if they were raw and dripping blood. 

If you want more information about Thai ingredients and recipes, I found a great little Chicago-based site here.