Marina Square
there are some buffer restaurants in marina square. you can go and have a look.
Japanese Curise, Sushi Buffet, international buffet, BBQ, steam boat, etc. all the price is around 20+-

还有
west mall Sakea sushi, think weekdays got buffetm, but the time is wield, afternoon only.
Suntec or Jp the fiesta Sushi..not buffet but 2 person $35 enought.

Marina Square
1. Breeks western food
2. 来一客 应该是和成吉思汗连锁的, although dinner is slightly more ex, but got more things to eat

Suntec international buffet below $20

JP 楼上那家上海翡翠小龙包也是不错 特别是云吞, 有四川红油抄手.

还有兴趣的话, 可以试一下Califonia Pizza, cheaper than pizza hut