Your salary is big enough for 2. House and car is main cost in Brunei, other than that...it cost u less. Living cost in Bandar is much cheaper than living in Kuala Belait (oil n gas town). You may save money a lot...however, it depends on your lifestyle.
You may apply dependent visa only for legal spouse or children because the immigration will need all the documentation for marriage. Your fiance may stay with you on visiting visa for certain period, so your fiance may make a 'u turn' before the visa expired to Miri or Limbang. I am not sure how many day given of visiting visa for Thai national. The process of dependent visa will take approx. 2 weeks to 1 month or less, depends on immigration.
If you want to buy a new car, you may need to work here at least up to 6 months for a bank loan. You may find a lot used car here being sell with good condition, just need to pick the right one. Some people advised to buy only Japanese car here, because of the quality, low price, low cost maintenance and its high value and easy when you want to sell it back. You may buy used car from agent or person directly, try this website bruneiclassified dot com.
Not sure about Armada Housing, i think it is quite costly, but again its depends on your preference. Thai community, i am not sure, but i bet they have.
Culturally Malaysia, Singapore are quite same. Just Brunei is more peaceful and not so busy as big town in those countries. Plus you will have peace of mind because of nearly no crime in here. If you have any other query, just ask, i will try to help you. Hope this will help you. Thanks.
