Thai restaurants and food stalls

Lan Som Tam Nua (or Som Tam Paradise) - A real Isaan restaurant in the heart of Bangkok. Traditional dishes from the North-East of the country such as Som Tam Lao (raw and spicy papaya salad) , Laab Moo (pork salad) and Khao Niau (traditional sticky rice). Most of the dishes are really spicy, so please be prepared. A haven for Isan people in Bangkok. Found at Siam Square, soi 4.

Seefah - Thai restaurant chain, with a restaurant represented on Siam Square. Traditional Thai dishes and cuisine as well as drinks.
Website: www.seefah.com

MK - Thai Suki Restaurants. A mixture between Thai and chinese food, often prepared at the table. Ingredients such as fish, mushrooms, seafood, vegetables, noodles etc. Various drinks and desserts are also found on the menu. Several MK restaurants are found in this area.
Website: www.mkrestaurant.com

S&P - Restaurant and bakery. Serves Thai, Chinese and international food, as well as Häagen-Dazs ice cream, desserts and cold/hot drinks. A few S&P restaurants are found in this area, of which one next to Siam Square.
Website: www.sandp.co.th

Chinese

Scala (Scala Theatre) - Chinese food, such as Peking duck, Shanghai noodles and soups in a classic restaurants that opened in 1970. The restaurant is found at the ground floor of the Scala Theatre, Siam Square.

MK - Please, see the Thai food section above

Japanese

Fuji - Thai-Japanese chain with a menu including salmon dishes, sushi, shabu, sashimi, futomaki etc. Several locations in the area such as: Siam Center, Siam Paragon, MBK and Emporium.
Website: www.fuji.co.th

Kobe Steak House - Coming soon
Website:

Korean

Koreana - Coming soon
Website: 

Italian

Focazzia (Novotel Bangkok Hotel) - This italian restaurant offers pizza, homemade pasta, antipasti, soups and salads, as well as homemade ice cream and sorbets. It is found on the basement of Novotel Hotel.

Spaghetti Land - Coming soon
Website:

Fast food

McDonald's - Serving hamburgers, french fries, soda and other fast food. Several restaurants are found in the area.
Website: www.mcthai.co.th

KFC (Kentucky Fried Chicken) - American fast food chain with deep fried chicken as the specialty. The chain has a few restaurants in the neighborhood. 
Website: www.kfc.co.th

Other and fusion food

Hard Rock Cafe - Food, beer, cocktails, music and entertainment. They are serving burgers, salads, sandwiches, steaks and desserts etc. Location: 424/1, 424/3-6 Siam Square, Soi 11.
Website: www.hardrock.com

Coffee houses

Starbucks - An American coffeehouse chain serving "regular" coffee, ice coffee, espresso, cappuccino, frappuccino, chocolate etc. It's possible to use internet if you bring your notebook here. There are several Starbucks found in the area. Except from Siam Square, you will find it on MBK, Siam Center, Siam Discovery Center and Central World Plaza.
Website: www.starbucks.co.th

Black Canyon - A Thai coffeehouse chain, serving hot and cold coffeedrinks as well as lighter meals. The chain has a few shops in the area, as in Siam Center and Central World Plaza.
Website: www.blackcanyoncoffee.com