One of awesome things about Thailand (and SE Asia in general) are the food markets and food courts in malls. There is so much good food to choose from and the prices are very affordable (specially if you go to local place and not 'for tourists').

The local markets with fruits and veggies are great. You can find all kind of fruits there that are local and imported (exotic, like apples and grapes). It takes time to learn how to pick the riped fruits or you can always ask somebody to do it for you.

First time we came to Vietnam we asked the hotel personnel to get us some seasonal fruits and they did so (didn't even want to get paid for the service, we paid for the fruits of course).

Besides the markets there are just fruit shops where they sell all the seasonal fruits too. You pretty much can always negotiate a better price (specially where tourists are expected to shop).

There are vegetables too, but it seems that mostly locals eat some kind of grass and potatoes etc is mostly a small addition to the dishes, potato is rarely used as a main player on a dish. We had to go to russian restaurant on the New Year to eat some mashed potato :)

some tips:

ask locals (who you trust) about:

• which fruits are in season now
• what is average price on particular fruits
• which is the best place to buy fruits (they will be fresh and tasty)
• shop from one place and bargain better price on larger purchases