Thailand in general, is not a year on year capital gain market. its a buy to live in or rental investment market, there are even specific taxes to stop flipping properties for profit. Thailand has one of the highest home ownership rates in the world, around 70-80%, and new stock is always being built so there is never a supply problem to push prices up.
Actual prices can often be the same as 10 years later. There are always stupid listed prices that are never achieved so foreigners see that as the market going up.
Foreigners often think the Thai market is just like home with percentage gains every year, and they often pay way over what a property is worth, only to find out years later they paid to much and have no chance of selling.