I have seen on many blogs and sites that it is ok to bargain when you are shopping.(minus preset retailers and merchants) Is it appropriate to bargain when it comes to food vendors or street markets? or is the price they have posted what is expected?

I would not say with food vendors. street markets selling clothes and other good then yes you must or you will end up paying silly prices. It is expected.

I was once told come down to a third and then back up to a half. not always the case. The longer you are thee the more you will get used to it.

Things like DVDs are aound 100 each and 11 for a 1,000.

At the end of the day it is what it is worth to you. I find in the uK now that many of our retailers offer goods at cheaper than the price in Thailand.
Do your calculations on the exchange rate right as well I see many posts where people say things like "we got accommodation for 600 bhat, Thats just £5.00" it is more like £10.00 so it is easy to misjudge.
another tip would be to go to somewhere like tesco Lotus early in the holiday and see what the prices are like there it will give you an idea of the set prices.
I think that every one of us falls foul of paying over the odds at the begining of the holidays.
Make sure that taxis are metered and always agree a price.

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Kiss
God laughs at people who make plans.

If you dislike the whole bargaining thing and don't like being ripped off all day long I suggest doing just about all your shopping at Tesco or BigC or Carreforre, prices are fixed just like at home, prices are low, usually lower that any shops or markets outside (which is why you'll see thousands of Thais shopping at these large super stores) furthermore you can bring back faulty good for a full refund within 7 days (try doing that at a market)
When eating at restaurants prices are usually listed with the dishes, however, if they are not you must ask how much everything is, or else you'll be charged more for being a farang. You see when Thais charge us extra they don't see it as a dishonest thing, they believe it is the correct thing to do, because they see their government charges farang 200% - 400% more that Thais at the national parks and major attractions.

Good point Bob about the government pricing structure.

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Kiss
God laughs at people who make plans.

You would never... never bargain about foods and drinks be it at street vendors or at restaurants!!

It's alright to bargain at any street vendors selling clothes, souvenirs, bags, shoes, etc. For myself I use to say that at places behind glassdoors I wouldn't normally be bargaining.

But... when you are bargaining you have to remember that these people selling things on the street are hard working people standing in the sun all day trying to make an honest living to make money to pay their bills and their kid's school and education, etc. That means that you should treat them with respect - as they usually are doing to you. Thai people are friendly people so bargain with a smile... it's okay to joke! Be reasonable with your bargaining, and don't talk bad about the things they are trying to sell - then it's better to just leave the shop... still with a smile on your face, it costs nothing to be nice. And do remember, at the end it is the shop owner that sets the price, not you!

I say all this from experience because my Thai wife is running a street shop, and we are every day met by a few aggressive and unfriendly tourists who don't understand the real 'game' of bargaining. Have some fun shopping around!

I would say that you cant bata with Thai's like you can in Bali with the Balaneese because the first price isnt as inflated as in Bali.

Thai people on a whole are honest people more so i have found than Europeans so if you try to bargain to low or too much they will say no with a smile.

You will know within a day weather you are getting ripped of big time but the small ones dont really matter,after all even when you get ripped of a little bit it is so cheap anyway that most time it doesnt seem to matter.

If you want to have fun while bargaining,when you are given a price just say"Cow sip cow baht" I dont know how to spell it in Thai but it means 99baht, this usually gets the vendors laughing and every time they see you they will remember and say "Cow sip cow".

Den.