There is no single monthly rate. Price follows headcount, shift pattern, guard type and what the contract promises. Here is how each one moves the number, and how to compare quotes fairly.

Two quotes for the “same” guard can differ widely because they are usually not pricing the same thing.
One post open 24/7 is not one guard. It takes several people to cover every shift, rest day and public holiday.
12-hour and 8-hour rosters need different headcounts and carry different overtime exposure.
Both are KDN-compliant. Nepalese guards are often more cost-effective on long 24/7 contracts; local guards suit client-facing posts.
Access control only is cheaper than access control plus patrol clocking, CCTV coordination and incident reporting.
Long-term posts (typically 12 months or more) are priced differently from event or ad-hoc shifts quoted per shift.
EPF, SOCSO, EIS, overtime and public holiday pay are legal obligations. A quote that ignores them is not a like-for-like price.
If a quote cannot answer them, it is not comparable.
A rate far below the rest of the market has to come from somewhere.
If contributions and overtime are excluded, you may inherit the liability or the shortfall in service.
Every guard should carry a KDN ID card and hold current CSG certification.
Operating without a KDN licence is an offence under Akta 27. Ask for the documents before you sign.