I need to buy 20 of those blackboard:where i can find them and how much will be the price?Thank you

looks like a school supplies comp sort of item to buy not sure but close by any major school /uni should be a good start

Silpaban sells blackbaords.

There is a store on Pattaya Klang just east of Foodland (same side) and another one on Pattaya-Naklua Road just past the Photisan Rd intersection on the left as you come from Dolphin Circle.

No idea of the price, nor if they have ones such as shown in your photo.

The open furniture shop across from Big C north sells them. They have a white board on one side and a green chalk board on the other side, with a wood frame with legs and a brace and a box for chalk on one side. Their price for 1 is just under B1000, and I expect that you can get a volume discount for 20 pieces. The smaller stationary shops sell them (one on Naklua at Soi 18(?) about 1 km south of the seafood market; opposite side) for about B1300. I bought one at the shop on Nakula and then saw the same thing at the shop across from Big C for 1/3 less.