Are you applying for that visa or do you already have it? Or are you an agent, or just collecting information? If you introduce yourself properly, it might be easier to answer your questions.
In my opinion, they are also looking at turnover. In my bank statement, it's clearly visible: the income during that period, the outcome during that period, and the ending balance.
They want to see if you have money that can be used and not just funds set aside for the visa. Basic requirements: a monthly (3months in Malaysia) bank statement with an ending balance of 500,000 THB or the equivalent in another currency.