How often can I enter Malaysia - US citizen with Singapore work permit

No rule about how often. The Singapore work permit and weekend pattern would indicate you are living legally in Singapore. Immigration is more involved with people who are attempting to live in Malaysia without a long-term visa - that has become problematic now with Do Not Land situations.

Thank you @Gravitas!  You're response is very helpful    Cheers!

Your partner can probably apply for a Dependent Pass for you in Malaysia as well.

Hi Gravitas, my girlfriend and I are not married yet.  Can she still apply for a Dependent Pass even though we are not legally married?  We have been living together for over 5 years.  Thanks!

There is the possibility for common law spouse to be provided with a Social Visit Pass (Long Term)

https://esd.imi.gov.my/portal/pdf/TC-ES … r-2017.pdf

Page 25

SOCIAL VISIT PASS (LONG TERM)
Eligibility criteria:
Children above 18 years old and unmarried of Employment Pass holder; OR
Parents & Parents-in-law of Employment Pass holder.; OR
Common law spouse of Employment Pass holder can be considered

Features:
Allows the holder to stay in West Malaysia
Employment is not allowed and requires conversion to Employment Pass
One (1) time application and change of partner is not allowed for common law spouse

Documents required:
Recent passport photo
Copy of passport (full booklet with cover)
Copy of Birth Certificate (for children above 18 years old) translated* into English
(if applicable) and Certified True Copy (CTC) by the Embassy/High Commission/ Consulate  General of respective country OR respective Embassy/High Commission/Consulate General in Malaysia
Copy of Birth Certificate of Employment Pass holder / Employment Pass holder's spouse
(for Parents and Parents-in-law) translated* into English (if applicable) and Certified True Copy (CTC) by the Embassy/High Commission/Consulate General of respective country OR respective Embassy/High Commission/Consulate General in Malaysia
****Affidavit / Acknowledgement letter from the Employment Pass holder's Embassy /
Consulate General on the relationship status (for common law spouse)****

The advantage may also be you can use the egate through immigration and potentially save time in long queues

Hi Gravitas,

This is very helpful, thank you!  My partner and I currently reside in New York City where common law marriages are not performed.  They do however, register couples as "Domestic Partners" which is very similar.  I will look into this as an option.  Thanks again for your advice & help!

-Brad