Hello Jirapat,

based on disciplens you've mentioned, there are 3 key areas in which you need to obtain fundamentals:

1. Basic Corporate Finance (valuation techniques)
2. Basic Financial Accounting (understand terminology like: Accounts Payable/Receivable, and be able to "read" Balance, P&L, CF)
3. Basic Managerial Accounting (especially i recomend to focus on cost structures and behaviours)

There are two ways to do so:

1. Available consulting preparations services which are FREE, and contain all 3 components and application frameworks in a single course (reasonable solution if you're quite short on time, pragmatic and quite practical; - however lacks some "academic" level knowledge).
2. Study your way more "academicaly" (Libby/Libby/Hodge for deep understanding of FA, as example), use services like OpenTuition and focus on Fundamentals of CFA/CIMA/ACCA.