I've been to Bangkok more than thirty times.

Since you have only two days, you will have to use your time wisely.
Which two days of the week? If Saturday and Sunday, try Chatuchak.
But Chatuchak, also known as Jatujak or "J.J.s" has 4,000 dealers...

It is hot and crowded and can be hellish -except when they play
the National Anthem and everyone is expected to instantly stop
and remain motionless in reverence to King Bhumibol Adulyadej.

If you have never been to Bangkok before, I feel it would be better to
try to relax and enjoy being a tourist. It's apt to be very hot and humid.
And, I can recommend places to shop. But do not expect it to be easy.

If you have enough money and expertise in ancient agate and "Pyu" beads
you will be able to make quick decisions and move on. But if you need to
deliberate and go back to the bank for more cash, you will most likely
become overheated and confused and have difficultly trying to find
your way back before other collectors buy what you thought you wanted.

You are likely to be competing for the best with rich Chinese collectors.
And most likely they will leave you standing in the dust…beadless.

Just Fred