This is a little gem in the Noge area! Opened 24 hours, the restaurant has a very different feel than most Thai restaurants in Japan. You'll see in the refrigerator that they have plenty of Thai ingredients that you can actually buy directly from the store. Many Thai people in Yokohama shop there apparently. The drinks are in a refrigerator from which you serve yourself, and you drink your beer directly from the bottle. As for the food, they have lots of variety from stir-fries, to curries to noodles and deep-fried foods. All are excellent, authentic and cheap!
In operation since 1990, Keawjal is a restaurant that has a total of seven branches including one in Yokohama's Minatomirai. It's known as one of the best because the food is authentic and the ingredients are imported directly from Thailand on a biweekly basis so everything is very fresh. It's very affordable too! Many dishes are under ¥1,000.
Asian Bistro Dai
As you might have guessed by the name, this place doesn't serve exclusively Thai cuisine but many other kinds of Asian cuisines as well. Everything is excellent and affordable. The decor, which is a kind of fusion of South East Asian and European is really stylish and the atmosphere is relaxing. You can enjoy a terrace in the summertime. They have all you can drink options for up to three hours! They have good cocktails and wines too. The restaurant is a bit secluded, located near the Hiyoshi station but is well worth the go.
At Boathong there are some fine lunch sets of either Thai fried noodles, Gapao, or Thai ramen for just around ¥1,000. These are served from 11:00 to 15:00. In the evening, many people go there and order a couple of dishes that they share with their company. It's a sort of Thai style izakaya. You can have a couple of Thailand's famous lager beer Chang and eat plenty and it shouldn't cost you more than ¥3,000 per person. This restaurant is located near the Kannai Station.
Thai Thani タイタニ
This place has an interesting rustic American Western interior that creates the perfect ambiance for a laid-back evening. The chef here is a Thai national so you can expect something authentic, although they can adapt their dishes to your personal taste by making them less spicy or not putting any coriander in them. They have a really good variety of foods. The Tom Yum soup and the green curry are supposed to be really nice.