I have two questions here but they're related. First, I'm hoping I can get some suggestions on phrases and words that I'll need to know in Thai. I do not speak Thai at all but I want to know what kind of things I may need to know how to say. I don't even know how to say yes, no, thank you, etc, so I really need some advice. Thanks!! :)

Along with that, I need some coaching on how to bargain with people at markets and stuff. I don't even know how to do that in English, let alone Thai. I need to know how to say numbers (what bills am I going to be using??) and in general how to haggle or bargain. Any advice would be oh so appreciated!

Much if the information you want you can get with a simple Google search.
thai currency photos - Google Search

Most of the currency you will be using will be (paper) baht 1000, 500, 100, 50, 20 and coins. Wait until you get to Thailand to change any currency over to Thai baht for the best rate. Most popular currencies can be changed 24 hours a day at Suvarnabhumi. Other bank branches and mini banks available with good hours every day in major areas popular with tourists that are not a holidays.

Last year 15 million tourists visited Thailand, most of them not knowing any Thai at all and they survive. Some words you should know are thank you and hello of course, along with some phrases for maybe "no spicy food, no peanuts (if you have allergies,) vegetarian, etc." Most of the Thais you will come in contact with will be able to speak enough English for you to get your point across. You should have no real problems with airlines, hotels, supermarkets, malls, Seven Eleven stores, McDonalds, bars and restaurants, etc. But you can also pick up a cheap English to Thai dictionary and just point to the word you want specifically and the Thai person can read the translation in his language.

There are some Thai words that foreigners will never pronounce correctly in a short amount of time. Hello and thank you will go a long ways!
Basic phrases
Common Words & Phrases - Learn Thai w/Langhub.com - YouTube

You only time you need to bargain is with street vendors and maybe a few private shops. Mall stores have prices listed, stores like Robinson, Big C, Lotus Tesco, etc. Supermarkets and Seven Eleven type stores have posted prices. For Bangkok you use the meter in a taxi. If you bargain the fare you pay more than the meter fare anyway. Tuk-tuks will cost more than meter taxis because you bargain the fare! Transportation from the airport is regulated.
Bangkok Airport Public Taxi Service | Suvarnabhumi Airport | New Bangkok Airport Guide
UrbanRail.Net > Asia > Thailand > Bangkok Metro

How to bargain - well if you stink at it at home you will still stink at it in Thailand! If you look like you have money the price you are offered may be more than another tourist who does not look wealthy! If you look rich you may pay more! If you see something you can ask what the price is. Move on to another vendor and see what the price is there. Sometimes you get a better price leaving. If you make an offer probably start around 25% of what is asked. If a vendor asks for 500 baht and you offer 490 baht that is not bargaining - more like being stupid! If you start low you can always raise your offer but if you start an offer too high you are screwed! Smile a lot, don't argue, stay friendly. But if a cheap item is going for 30 baht or 50 baht you won't get it for a few baht. Be reasonable.
How to bargain
What is the best way to bargain in Thailand?: Asia travel FAQ

Have fun.

Branded supermarkets, department stores, convenience stores, and the like, aren't into much bargaining. Usually, the best one can do is score set up and/or delivery.

Restaurants, food carts and shops have set pricing.

Most everything else is, pretty much, fair game.

I don't waste too much time as a lookie loo. If I am checking something out, it will be something I want.

Showing interest, while keeping silent, is my approach. I will let the seller become interested in me. Make them sell it to me. After they set a beginning price, keep "thinking". Often they will start the negotiations. I will decide what I want to pay and then work towards that.

When it comes to 40~50 baht items, these are often things one can use a few of. Often, you can try offering 100 baht for (3) 50 baht items. Go for the "buy 2; get 1 free" concept. Work from there.

Bottom line is to keep it friendly. Shopping is a social activity in Asia. And, if you spend a lot of the vendor's time, driving a hard bargain, getting a substantial price cut, don't walk off. Buy the thing.

And rest assured. After you have bargained your heart out, got the best deal ever, you will find the identical item for less at the very next stall!

Sometimes the best price you get bargaining is the price you think you get!

And usually the best price is at Tesco Lotus, Big C, Carrefours etc.