1) When one applies for Online Banking as well as a MasterCard at a Thai or Cambodian Bank, what (standard) procedure does the bank follow?

2) Does a Thai or Cambodian bank inquire, or does it have the authority to inquire about the financial status of the applyee in his/her native country?

3) Is the information that one has an Online Bank account and a MasterCard at a Thai or Cambodian bank being kept private, or is this information publicly registered, somewhere?

Do you have a work permit?if not you don't need to think further,because almost impossible to get a credit card without a work permit,some banks let you deposit some money into your account,for example you must deposit 150000bt to get a get a 100000bt limit on your card.

2) Does a Thai or Cambodian bank inquire, or does it have the authority to inquire about the financial status of the applyee in his/her native country?

3) Is the information that one has an Online Bank account and a MasterCard at a Thai or Cambodian bank being kept private, or is this information publicly registered, somewhere?

No, they won't call to your home country to verify your details.

As previously said, without a work permit, and I believe 3 to 6 months into your job in Thailand, you won't get issued a credit card.

And you may be only able to apply for a secured credit card (where you keep a deposit of the limit you want on the credit card)

Keep this in mind:

"Thailand does not have stand-alone secrecy laws. However, the new Consolidated Financial Act in 2008 has a provision providing for bank secrecy to prevent disclosure of client financial information. The new act includes some exceptions, including investigation by a financial regulator and any memorandum for understanding committed with other domestic and overseas regulatory agencies on financial institutions or financial transaction. Therefore, financial institutions must disclose their client and ownership information to AMLO upon demand."

So, if you American for example, the IRS can easily obtain all your banking information.