From my understanding, whether your income is above/below, as long as there is income, it is the individual responsibility to declare the income, even if you earn RM10 per month (=RM120 p.a.).

You will still need to register, request BE form, fill up RM120 (penggajian), then RM8000 personal relief.
Hence, taxable amount = 0
Tax payable = 0

But a lot of people have this Tidak Apa attitude, say below RM30k no need to declare, don't waste time fill up form, etc.    Later when get caught/audit, make a lot of noise say govt is stupid need to declare this lah, that lah   

They do random audit lah.   
I kena before, but nothing to scare, as I have everything in order including receipts and explanation. Just like going to interview and show your certs, etc. 

hi, just worried if the income tax people will hassle me cuz i just bought some property that may be over what i reasonably can save from the declared amount. how much do they assume you could save from the declared amount? 50%? for example i declare i earn 100k but i buy a house with downpayment 70k would this give them a good reason to question me?

thanks

No other reason, they just random pick me. I asked them anything, they say nothing specific. They did not ask any weird questions or deep probe also. Just ask mana receipt ini insuran nyawa ? Apasal tak declare bulan November XX (cause in between new job after resign, show them EPF statements) Mana receipt donation ini ? Mana slip resit bayaran income tax tahun dahulu ?
Even if you declare 100k, but buy a house at 90k cash, LHDN may question how you survive on 10k PER YEAR. It is possible to survive on less than that, but they'll ask you further or for you to prove to them. They may ask further questions like your car loan, your dressing (armani on 10k per year?    ), etc. If you say pay car cash that you buy last year, then   

90k house (cash) + 50k car (cash) = 140k cash > 100k declared income.