Fortunately I've never had a hankering for Western food here and I think after three years in Thailand I've forgotten what the inside of a supermarket looks like. There is a wide selection of fruit and veg available from the plethora of local markets.
You're living in Thailand so learn to speak Thai. Even if it's just enough to do the shopping. If you were back in the Old Blighty, you'd be screaming about people who dare to come to England and don't speak the language. Same goes for you sweethearts. Show the same respect you'd expect and learn some basic communication.
Street stalls are great but be careful with the sugar and salt. Much more difficult to fix when soups are involved. However, freshly cooked veg and rice meals are easily solved.
Mai sai pong chew rot - no MSG.
Mai sai nam daan - no sugar.
Mai sai khem - no salt.
Nam man nit noy - just a little oil.
Try some of these phrases when you are ordering and hopefully it will help you to eat healthier. Or at least avoid some of the bad sides of the Thai food. They do go OTT with the sugar, salt and msg so you have to cut that when ever you can.
Apart from that the wonderful variety of fruit and vegetables make for wonderful eating. There are a few good Thai cooking schools around that can help you learn about the different ingredients.
Please head to your local market and try the plentiful, cheap varieties even if you only slowly expose yourself to new things. There are plenty of cheap, familiar varieties to chose from. Above all else learn to eat Thai. Eating western is far too expensive in this country.