Four Kings, by Christopher Sun, or The Forlorn Adventure, a sci fi novel by Amir Falique. Four Kings is a murder mystery set in France - besides the fact that I have not seen a good review of it, neither novel seemed likely to enlighten me much about life in Brunei.
Then I stumbled on a reference to K H Lim's Written in Black, which seemed much more like what I was looking for. The narrator of this novel is ten year old Jonathan Lee, who is attending the funeral of his "Ah Kong" (grandfather). Jonathan's mother had left for Australia six months previously. His elder brother Michael has been kicked out of the house and has joined a rock band. Jonathan is missing his mother and when he finds out from his cousin Kevin, that she has been in touch with Michael by telephone, he escapes the funeral (a traditional Chinese funeral lasting several days) in an empty coffin in the back of a truck. His quest to find his brother and thus contact his mother leads him to encounter poklans (teenage delinquents), derelict houses full of bats and weird shopkeepers.
It's a fairly unsophisticated story and the idea that a ten year old is narrating is not quite convincing - the voice of the narrator is a little too self aware - more like an adult narrating a ten year old's experiences. Nevertheless, it is an enjoyable story. I was surprised to find that Jonathan's family all had western names, and there was plenty of mention of Western culture - a mother in Australia, New Zealand gardening programmes on the television. This would not have suprised me had it been, for instance, Singapore, but I knew little of Brunei other than that it is an oil-rich country ruled by a Sultan, so I was expecting something a little different. Still, other aspects of the story were definitely not western.
K H Lim was born and raised in Brunei. He graduated from medical school in the UK in 2008 and currently lives in Singapore. Written in Black was published by Monsoon Books in 2014.