Am I correct in thinking that the price per baht shown on the digital boards inside/outside shops is the 'bullion/ingot' price? It can often fluctuate by a few hundred, even thousand(s) baht from time to time. There is a premium applied to buying necklaces/bracelets/rings etc due to the workmanship involved?
When selling/upgrading an item of jewellery I assume you get the bullion/ingot price minus the 'spread' (usually around 100 baht).
Also, in response to one of the OP questions - Thais love a bit of gold. They view it as money in the bank. When times are hard, very easy to pawn/sell an item. Tends to hold it's value very well and most likely increase over time.