Peter Ng Sending money from abroad to Bangkok Bank for example shows as "FTT" (Foreign Telex Transfer) in the bank book record. This is evidence that the money came from abroad. However, I am not sure how other Thai banks handle that.
For a joint bank account you have to show doubled amount i.e. 1,600,000 Baht instead of 800,000 Baht. Or you open a separate bank account with your name only.