Mae Sot has such a rich diversity of cuisines on offer that you should be able to find pretty much any style of food to satisfy your craves. Burmese dishes are popular, as is Italian, and there are plenty of cheap noodle shops and side cafes. If you really can't find a restaurant to suit you then there's a huge Tesco Lotus supermarket that's loaded with fresh goods.
Bai Fern is busy most nights which is always a good sign. The NGO factor of course helps the numbers, but it can't be denied that the food is pretty good. The menu is huge and contains half a dozen different cuisines from local curries to steak to lasagna. A steak will set you back around 250B depending on the cut and a pasta dish in the region of 120B. It must be said it's not the cheapest restaurant you'll visit and the SP Kitchen outside town served cheaper and better Italian food, but if you want diversity you can't beat Bai Fern. The staff are extremely efficient and most speak fluent English; they can also help you with travel plans and renting motorbikes.
For the finest Burmese east of the border, drop by Aiya. From the outside it doesn't look anything special, but order some food and you'll see what is so special about it! The walls of the outlet have artwork hanging which has been painted by local artists, and the upper floor doubles as a sort of mini gallery with some interesting pieces, particularly some stunning water colours. Their Penang curry (80B) gets a major thumbs up, served with brown rice and a roti if you choose; there's also Red Green and Massaman curries. It's not only the taste of the food that impresses, but the presentation is also more suited to a Royal Thai restaurant in a posh hotel in Bangkok, which makes the budget prices even more surprising.
The main road is quite an odd location for the best Italian restaurant in Mae Sot, but if you're willing to make the short journey out to SP Kitchen then a reward awaits. The restaurant itself doesn't exactly replicate an Italian Trattoria, perhaps more like a thai style beach shack; nevertheless, the food more than makes up for the mediocre decor, and the prices attached are truly good value. A huge lasagna will set you back only 75B, served with salad. A four seasons pizza is 110B and the drinks are equally budget priced; if fact its such good value here you wonder how they make money. SP Tour on site organises trecks to Umphang and some local attractions, but its very commercial and serves package tours mostly.
There's nothing particularly special about the menu at Fah Fah, but it does serve a good range of Thai dishes at very competitive prices. The place is set out like an American diner more than a Thai restaurant, with clean booth style table and benches. A fried rice will set you back only 25B, and a chicken with cashewnut stir-fry is 60B. If you don't fancy Thai there's some western style salads, and for the sweet toothed crew there's a large ice cream sundae menu. A decent no-nonsense option.
Mae Sot seems to have a decent live music scene and you'll find it easy to locate a bar and lounge back to some chilled out music. Down by the entrance to No. 4 Guest House there's 'Cool Bar' which although not large manages to cram enough people to create a decent atmosphere; they alternate with the equally small 'Folk Song Bar' next door which also hosts live music. Both sometime carry the party on until the small hours so no need to get there early. Another place is Thaime's Bar, about 100m east of Bai Fern restaurant. Formerly known as 'Crocodile Tears' this place has long been a popular haunt with locals and foreigners alike, and as it's probably the largest bar in town it's always going to be busy as the night rolls on. The band start cranking out the music at around 9pm. Next door the Blue Moon Bar is more of a local scene and the true late-nighters often end up at Lucky Music Bar in the centre of Mae Sot.