HI! i am interested in regular course for mba in Malaysia. english is okay as instruction language. i am wondering about the safe bets with regards to teaching and reputations.

I couldnt find any of the Malaysian schools in any of the rankings, so it is a little difficult to help you.. Hm, does anybody know of Asian/Malaysia related rankings?

Malaya UMGSB should be safe. It's AMBA accredited.

http://find-mba.com/schools/asia/malaysia/malaya-umgsb

There's also a school called Universiti Putra Malaysia (UPM), which holds AACSB accreditation.

There some other good schools in the region. Here's some more info:
http://find-mba.com/articles/mba-programs-in-southeast-asia-tapping-into-the-tiger-cubs

The two that Alain pointed out are both really great options. However, I do know that many Malaysians go out of the country to do their MBAs: Singapore is a good hub for this, and top schools like Nanyang, NUS, and SMU all have decent connections with Malaysian employers.

Some best MBA Universities of Malaysia are:
Universiti Malaya - University of Malaya Graduate School of Business (UMGSB)
Universiti Putra Malaysia (UPM)
Universiti Teknologi Malaysia (UTM) - International Business School
UCSI University Malaysia
Universiti Sains Malaysia

How do the Malaysian MBAs and Singapore business schools compare to the international MBA programs also offered in Malaysia, like Nottingham and Westminster?

I'd say that they are pretty comparable, if you are looking only at the internationally-accredited business schools.

However, the ranked Singapore programs, like Insead, NUS, and Nanyang, probably have stronger placements (higher salaries) and more robust networks. I suppose though, it depends on what exactly you're looking for.