Tips are heartily given. Regardless how much you give surely it will be appreciated. Remember those people are working by small salary so any help can make a difference, not much but it helps.

If you're an American you might find it hard to break the habit of tipping but tipping is not a custom in Thailand; the Thai don't tip, they haggle. For example, market stall sellers offer goods at a higher price than they expect to get and it's up to the buyer to try and get a better price.

Be careful about taxi fares, some drivers are very honest (I hear that it's the driver's of the shiniest, newest cars who are the most reliable) but some will hustle you for an inflated cab-fare and charge you double the price.

As a foreigner you will be expected to pay more for some things than the Thai would pay; bus fares are doubled for foreigners (all foreigners are rich!) but this is normal, consider it a built-in tip.

Some Thai can get greedy about tips and may brazenly ask you to give them a tip when they haven't even done anything, don't pay anyone a tip unless they have given you extra service deserving of a tip.
It's up to you how much to tip but remember the Thai don't pay anything.

I good appreciative tip to leave is 20 baht which is the polite thing to do but it is up to you if you want to tip or not. The most I would tip extra for massage would be 40 Baht
Tuk-Tuk public transport you do not normally give tips but if you want to it's up to you - no one will force you to give tip.
When I stay in Hotels I make sure that I see the maids who clean my room and give them 100 baht.

I good appreciative tip to leave at the restaurant is 20 baht which is the polite thing to do
massage 40bath
hotel 80-100 bath
taxi and tuk tuk dont actually except tips
up to u

Dont be so miserable

give what you can and help them out Taxis dont need tips but you can if you want
a lot of hotel workers depend on tips to build up there salary and it makes them happy and therefore will make you happy
What goes around Comes around ok what is nothing to you is a lot to somebody else
I was with my GF in a Shopping centre I bought something off a stall and the price was 990 baht the girl gave me the change I said no and gave it her back MY Ex GF then went crazy to me later saying no tot do that I said she was nice and why not But to her 10 baht was a big deal
Whenever I buy anything or get a discount from anybody or bought my GF etc I always give back some of the discount Or when they give me back I say no its ok Because to me 20 or 100 baht is not that much to them its 2 or 3 hours work
be considerate and make people happy ok Whats a few hundred baht in coins in your luggage when you get back worth to you : )

10 days to visit all those places? I say take a month over there. You need 3 days min for BKK alone and 3-4 in Chiang Mai, good luck with the rest.
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10 days doesn't give you a lot of time to just get from A to B to C. You might want to consider scaling back to just 2 points of interest, or, stay for a much longer period of time.
My first trip to Chiang Mai was suppossed to be 4 days. I liked it so much that I spent 11 days there. Get the picture? It's better to get more out of one place than to try to cram in too many destinations.

For a great time.Khao Yai national park to see the most wildlife in the country(it's where they filmed Leonardo DiCaprio jumping off the waterfall in the movie 'The Beach'),Ayutthaya,Lopburi and Sukhothai to see Thailand's versions of Angkor Wat in Cambodia,Bangkok for super cheap shopping,The Andaman sea for the most beautiful water in the country,The northwest mountains with Chiang Mai,Mae hong son,Chaing Rai and Phi for cooler weather,beautiful views and amazing temples.The Isan for very traditional Thai/Laos culture,Nong Khai to see the famous Mae Kong river and last but not least..The # 1 island is Koh Chang.It is across the gulf from Samui on the Thai/Cambodian side.If you are looking for an island to see then I strongly suggest Koh Chang.You can take a bus there from Mo Chit bus station,Bangkok.I have lived here in Thailand for years and have seen at least 90% of the country and have seen almost all of the islands.I consider it to be the most beautiful island in Thailand.Koh Chang has everything a person could be looking for in an island.It is the second largest island in the country,it has the largest cloud ringed mountains of any island here,only one side is touristy(but not too much)and the other side is almost people-less.You can feel truly cast away while standing on secret white sand beaches being the only people around.The touristy side has a law that restricts any building to be built over 3 stories so it does not have the ruined Honolulu,Hawaii look.Koh Chang has accommodations to fit everyone's budget.From a few bucks a night for a bamboo bungalow with only a fan,perfect $12.00 a night rooms,to way more than most can afford.It has full moon parties like Samui,excellent live music bars,incredibly good/cheap seafood/snorkeling,scuba diving on the outer small islands and because there is only one main road that circles the island 90%,the interior is completely wild.Most tourists come and go from Koh Chang thinking there is no wild life but that is because they hang around the coast all day and the animals have split into the mountains.If you go elephant trekking you will see plenty of wild life.Also,if you take my advice DO NOT worry about finding a place to stay prior to going there.White sand beach,Kai Bae and Lonely beach are guaranteed to have plenty of rooms available when you come(Unless it's the Song Khran new year festival time in April).The first place you will see is White sand beach it is the most expensive area to stay in but still has all kinds of normal backpackers partying there.My Thai friend Moe has the largest bar on the island in White sands.It is called 'Sabay bar'(Google it).Every night there is live western style music and sometimes on the beach concerts.The bar itself is also beautiful.In White sands you can find plenty of places that are also not overly expensive to stay in.The next location is Kai Bae where things start to get better priced.There is tons of really good western style food to eat in Kai Bae when you get really sick of rice like me.There are many,many bar/clubs there.My friend Nick from London owns 'Lek bar' in Kai Bae.It has good/cheap rooms and live music everyday plus excellent western food.The next place is Lonely beach.It got that name because years ago it was just a quiet,tranquil little place to relax.Then every rasta,dread lock person in Thailand found out about its very tolerant atmosphere and came there,now it is the Jamaica of Thailand.All the bars pumping out reggae.On from there there is Bang Bao.It is like a little town built out on the water.Where ever you walk the ocean is under your feet.It is full of sea food restaurants and tons of shops.I have barely covered the fun you can have on Koh Chang,there is just too much to do.You just have to see it for yourself.I have been there 30 something times because my Thai wife's family has a restaurant in Kai Bae so it is like a second home for me now.I often go wild boar hunting with her father in the interior and take people to the coolest places on the island that are far from the tourist ares.There is a place I found some years ago that even some of islanders did not know about I call 'Secret beach' if there is anywhere in Thailand like the little hippy commune (minus the hippies)in the movie 'The Beach' it's my little "Secret Beach."There are only a few fisherman's huts and the greatest beach I have ever seen in this world and I have traveled alot.The best part is there is a small river then comes down out of the mountains that backs up against the beach creating a large pool and then flowing over and on into the sea.The pool and river are perfectly clear with white sand bottoms and best of all,cold because Thailand is hot.When I go with tourists that I often show around the island who want to see the real Koh Chang they freak out when they see the beach.
I hope you take my advice you won't regret it.
Have fun in Thailand.

First of all, since you only have 10 days, I would recommend flying to Chiang Mai from Bangkok and staying in the city for about 3 - 5 days, then fly back to BKK and take the 3 - 4 hour bus journey to Koh Samet - (check out the link i've provided for times). Spend around 2/3 days there. That leaves you with about 7/8 days left, you could see Ayutthaya - there are buses and trains from Bangkok which will take you there - the journey is around 1hr 30 mins by bus.

Either way you are going to be pressed for time with just 10 days to see these places - remember, you won't get a chance to settle down for too long and you will need to make a schedule and stick to it if you want to go to all these destinations.

These links should be of use to you:

http://www.1stopbangkok.com/getting_here/bus/
http://wikitravel.org/en/Ayutthaya#Get_in
http://www.bangkokair.com/

Like other said, 10 days is not enought :)
1) From BKK to Chiang Mai by plane airsia / bangkokair/ nokair - spend 3-4 days visit temple, hilltribe area, elephant riding, bamboo rafting and if you like to see (old) temples - Sukhothai is 2-3days recommeded! - can go there from Chiang Mai by bus or train -
2) From BKK to Ko Samed (3days) by bus and connect to ferry. Have to get into the bus from Ekkamai Bus terminal (in down town) Or visit Ko Chang (4Days), by taking the bus from BKK Airport to Ko Chang directly. about 3.5hours away from bangkok.
3) From BKK to Ayutthaya by train 1.5 hrs. you can make a one day trip in ayuttha by hiring tuk tuk approx 350-500 per day, or rent a bike at touristim office at the train station.
4) Visit Bangkok old town area , plenty of temples are waiting for you to explore !

See the link below it could help you organize your trip easier. Have fun! :)