Overall, I would say your pricing is on the cheaper side of what is usually quoted in PJ

There are rules and regulations that has to be followed for electrical installations. Some are technical based (like the size of a wire for a given load) some are safety based (like having a 10 mA RCCB for wet areas) and some are arbitrary (like all water heaters should have a minimum wiring of 4 mm²)

Let's expand a bit on the 4 mm² requirement for water heaters; an installer might try to convince you that your WH is only 3000 W so 2.5 mm² wire can be used as the current flowing is (3000W/230V = 13A) under the wire limit of 20 A. So this is an arbitrary requirement from ST. If you know what you are doing and accept the risks and consequences, then by all means save some money and use 2.5 mm² wiring. My professional opinion would be to strongly recommend you don't cut corners though.

(Aside for a complete look at the issue : The requirement for 4 mm² was introduced in 2000 (I think?) so there probably are millions of WH installations using 2.5 mm² wiring with no issues. They also do not have that 10 mA RCCB protection, again with no issues. But both of these are statutory requirements now)

In conclusion, follow everything that is stated as a requirement in the ST document that you downloaded, and do not hire any so called "electrician" who tells you otherwise.

Well, with cert doesn't mean do things the right way, and without cert doesn't mean things are done wrong/badly. This is M'sia so anything goes like chicken farmer (That's poultry, not anything other.....) from Indonesia coming here and becoming the "Kepala" at construction site.

So you have to decide based on other people's recommendation or from gut feeling

Sure. But no need to ask who as he is also very choosy about customers. Not worth his time to layan all the lousy customers and end up with plenty of headache.

Sorry la, I introduced his number to a few members in LYN before, but he already tell me not to send his number to this board. He say here members always talk like millionaire, but in the end compare price with PATI worker then complain to him his price too expensive.

I think you are mistaking contRactor for contactor