If people bring Cash and want to use it towards the purchase of a Condo or to get the retirement Visa requirement of 800,000 in the bank, can you get a letter from the bank saying the money originated overseas, when you are going to the bank with Thai Baht already changed in the money changer ?

Can you get a letter from a Money Changer?

Will the Bank issue a letter stating it was foreign currency if you change it with them?

Seems that going to a money changer or direct to the Bank can save thousands of Baht with large ammounts of cash as opposed of going through the banking system.

No. How would the bank know the origin for cash? You could have used local baht to buy pounds to change back to baht at the bank.

Seems that going to a money changer or direct to the Bank can save thousands of Baht with large ammounts of cash as opposed of going through the banking system.

In my experience(I had to do it some years ago with 2M Baht),you lose a very high amount to the Thai Bank;I wouldn't recommend it.