When you arrive in Thailand with an important amount of cash, you should declare this funds to the Thai Customs, if the amount is exceeding $ 20,000 or an equivalent amount in any other foreign currency.

Normally, you can not import large amounts of Thai Baht, since exporting Thai currency is prohibited.

When leaving your home country with a big quantity of cash, you should as well in many cases declare the amount to the Customs. For countries such as France, UK and many others, an amount of cash exceeding €10,000 should be declared to the Customs when leaving.  This limit is applicable jointly for all persons traveling together and having a community of interest, for instance a familly. In practice, if you are traveling with your wife and children, the limit of €10,000 will include the total amount corresponding to the sum of the amounts individually held by each member of the community of interest.