Thoughts on dual pricing
Dual pricing is morally wrong and according to some experts on Thai law, even illegal. However, as with a lot of things in Thailand I question the apparent illegality of it, given how widespread it is I doubt it's illegal at all.
Now when it comes to dual pricing, we need to distinguish between opportunistic greed (like when a taxi driver refuses to turn on his meter or a tuk-tuk driver tries to charge a huge amount) and institutionalized dual pricing at tourist attractions. It is easy to avoid the former - either catch a different taxi, rent a car, catch a bus, walk whatever, there are always alternatives.
However, when it comes to a temple, museum, national park etc. trying to charge a foreigner more, there are two prices only: one Thai and one foreign. Occasionally a foreigner can get the Thai price by speaking Thai, arriving with a Thai spouse or friend, showing a Thai driver's licence, work permit, tax ID card or similar, but these don't always work.
The very premise of dual pricing however is that it tries to create a feeling of "us vs. them" by making assumptions about a foreigners perceived wealth. It is one thing if one time tourists are affected as they can just decide never to come back to Thailand and many do vote with their feet and their wallets. However, apart from avoiding all dual pricing attractions in Thailand, it is not as easy for resident expats to do the same, as they may be faced with this issue on a regular basis.
Personally I have no problems with bargaining, though on a day to day basis I only engage in that part of the economy that has fixed prices. For example, I drive my own car, fill up my tank at a petrol (gas) station, which obviously has fixed prices, get my car serviced at the dealership, I eat at chain restaurants (or independent restaurants with air-con), shop at supermarkets and hypermarkets etc. just like I would do in the west. Not only because this eliminates the possibility of dual pricing but these types of businesses offer better quality food, produce and goods and I know whether I'm getting value for money or not.
Also, it's easier to find what I'm looking for. Yes I know foreign imported goods are often way overpriced, but there is often little way around that except for the occasional trip to Cambodia to bring in a few bottles of cheap wine. The Thai alternative is poor quality rubbish, so there's little choice but to pay these prices.
I don't visit markets, street food stalls etc. unless I'm on holiday and that would entail being outside of Bangkok or more likely even, when I travel to Laos/Cambodia/Vietnam/Myanmar etc. countries which have fewer supermarkets/hypermarkets etc.
Why don't I visit markets etc. (except for very occasionally Chatuchak)? Because 1) it's hot 2) the quality is poor and unless I'm looking for a souvenir I won't find anything interesting 3) the food at wet markets is often of questionable quality - food and veggies may have been tainted with formaline whereas at supermarkets it's safe too eat, while at food stalls it's too hot to eat outside plus the food doesn't taste good, nor is it fresh in many cases. I am worried about getting sick.
I'd much rather enjoy a delicious steak from Sizzler, along with some salad, which is much healthier than the MSG and sugar laden crap you get on the street. I can also pay by credit card as I don't always carry enough cash with me.