That is what you get when your answer like this: "yea 1800? month you rent !!! .... "
But lets go a bit deeper into your business plan for furniture sales.
You want to have a couple of stalls:
Will you be your own competition or spread your furniture over these stalls?
Mostly people who have a stall are their own boss so have less cost than you. It is not easy to find and keep good staff here. Where are you going to find them? How will you employ them, will you have a regular business or pay them without any social security and tax?
How will you know they will actively sell things or be asleep / playing with their phones?
What do you arrange for lunchtime, do you have a fan there for them? What will be the electric costs?
I don't know the market itself too many people and too hot for me don't like to walkaround in busy crowds. Can you store your furniture there or do you need to bring it to your stalls every day (which is a major pain)?
Why would people buy from you and not online?
How are people expected to take the furniture with them?
How long do you expect it takes to buy new stock and get it into your stalls?
How do you keep your furniture in good condition if you have it in the market 24/7?
In a market people want to haggle about the price, how do you arrange with your staff what price they can sell and how will you know they won't pocket any money from you?
What will be your customers for furniture? Tourists, local Thai people, expats or .......?
Furniture takes up a lot of space, so you can't have many items in your stall. What do you think will be the turnaround time for your items.