Gold bars (bullion to you) usually comes in 1 baht, 5 baht, 10 baht. These usually need to be ordered through whatever Gold shop you choose (maybe 1-2 weeks to receive them). As someone else suggested, always keep the receipts/paperwork on the purchase. At todays prices you are going to pay about 390,000 baht (money) for a 5 baht 9weight) bar.
This is the way I buy Gold..2 x 5 baht bars every year since 1993, and will continue to do so. Now worth nearly 12m at todays price.
Just something for my daughter.