@Karol ***********
There is indeed no six-month rule. Some people get questioned after just two entries, others sail through again and again for over a year with no problems.
However, if you've already been here six months on short-term stays, you're in the general area where there is an increased likelihood of being summoned to the office in the back and questioned as to what you're doing here.
As John Stanners said, you can still get questioned or denied entry at the airport or land border even with a tourist visa (the former happened to me before). While there is indeed no limit on air-entry visa-exemptions, if you've got a history of just going out and back, repeatedly, then the likelihood of being questioned or denied entry goes up. It's all up to the imm officer.
All you can really do is have the three proofs mentioned with you. If you're applying in KL, you need to submit the three proofs at the embassy to get the visa in the first place anyway.